Girl thinks I’m a virgin but I’m not

So me and the girl I’m dating was talking about body counts and she told me how many people she’s had sex with then she asked what my body count was.
I made a joke and was like “none I’m a virgin” but she took it quite seriously and then I kept joking about it like “Yeah, I’ve never had a gf in my life” but I was saying it in a joking / sarcastic way planning to be like “haha kidding not really, I’ve slept with X girls before” but she took it so seriously that I felt it would be awkward for me to say it was a joke.. so just kept quiet and figured it would pass and forget about it
However it’s now been over a month and she regularly talks about how happy she is that I’ve only slept with her etc and she was so super serious about it that if I tell her I was joking it wouldn’t be funny anymore.. I actually feel it could cause a massive argument if I tell her.
Not sure what to do? Should I just forget about it and go along with it? Or just tell her I was joking in the future once we’re in an official relationship?

Keep schtum. Previous sexual history is no one else’s business unless you choose to share it

how can she prove if you’re a virgin or not??? just lie bro

She asked. He lied.

She asked. He lied.

You won't bring up the subject of your body count. The next time she brings it up you'll say something like "Well, actually." in a humourous tone. And if it then gets into a serious conversation you will maintain your good mood regardless of the mood she gets into. You won't apologise for what you did, because you're not going to let her conquer your humour. You should show empathy towards how she feels about it. But it should be empathy with a core of assertiveness from you. You enjoy throwing humour into conversations. It's just the way that you are. So that you may well give her a warm and gently hug as she tells you what a rotter you are.

Don't let her conquer your reaction by you falling into her frame that you've done something wrong. Maintain your frame that you've just been you. And that all this is just one of those things. No big deal in the grand scheme. And that similar episodes may happen in the future.

I could potentially see the merit in this if it wasn't for the fact that, according to the OP, she is regularly bringing up how happy she is that he has only slept with her. He's also said that she's so "super serious" about it that if he tells her he was joking it wouldn't be funny anymore. In other words, whether we call it a lie, a misunderstanding, or an attempt at humour that missed the target, the problem is that the OP has allowed this to build up in her mind to the point where it's now an important feature of their relationship for her. Even if don't think the initial joke is an issue, which I could understand, him allowing her misunderstanding of the situation to perpetuate is an issue. The whole "if she reacts badly she's not the girl for you" thing is such a poor excuse. He is actively allowing a situation to be maintained that is ultimately damaging the trust between them. A month is nothing in the grand scheme of things and it may well be that they aren't ultimately compatible. But that doesn't avoid the fact that he has handled this poorly, and if he likes this woman and wants to pursue things further with her, he needs to correct this misunderstanding as soon as he can.

You have distorted what I said when you said "The whole "if she reacts badly she's not the girl for you" thing is such a poor excuse"
What is said was "If she were to dump you because of this whole episode, she's not the girl for you."

You have a point. Although perhaps he was a tad ambushed with the question. If it has no material relevance to the here and now I think it’s acceptable to let the moment pass

Presumably we can agree that her dumping him would be a bad reaction, in which case I'm not sure what you're driving at. Even taking your original wording, my original point stands that the whole "if she dumps you, she's not the one for you" is making excuses, as frankly is the suggestion that she's made mistakes here too. She's misunderstood something. He knows she has. She doesn't. The power to remedy this lies with him, not her. Suggesting that some of the issues lie with her (the majority of them, no less) is, again, an attempt to make excuses.
People can choose to continue with or move on from relationships at an early stage for a whole host of reasons. It's not about whether they're each other's true love at this stage, and we all make mistakes. But if the OP has done something wrong the way to remedy it is to deal with it, not be blasé about it and then say that it's effectively her problem if she dumps him for it. If he wants to continue this relationship, he should correct something that has clearly become a reasonably significant thing to her.
Again, I know that you don't think it's important. But for all the talk of strategy and tactics when dealing with issues, and this quite weird desire to put one of three different labels on every single guy, the fact is that if you know something that you have done is going to bother your other half when they find out about it, the correct thing to do is to address it. Not because it's important to you. Because it's important to them. That is how things work in actual, established, successful relationships. If the OP thinks he might want one of those with this woman, it's probably best to start acting like it now by addressing this.

"the fact is that if you know something that you have done is going to bother your other half when they find out about it, the correct thing to do is to address it. Not because it's important to you. Because it's important to them. That is how things work in actual, established, successful relationships."

Wrong, wrong, wrong, wrong wrong!
Going back to the Saturday evening example. The Positive Challenge guy knows that their girlfriend wants to be with them on Saturday. And that it is important to the girlfriend. And that she will be bothered that he's off playing 5 a side instead of going out with her.
Should he address it? No! Not on your Nellly!
He should stick to his guns, play football as usual and see her some other time.
Should he be apologetic about it? Only very minimally so.

Will this make any woman (worth being with) love him any less? No!
It will actually make her more interested in him and more attracted to him.
Because of human nature.

The same principles apply to the original poster being the sort of guy that uses spontaneous humour. That sometimes gets misinterpreted. Should he stop coming out with those sorts of jokes? NO!
Should he apologise about the whole thing? Only minimally.

Your five a side football example is completely different to this situation, and a completely different issue within relationships, but if you can't see that there's no a lot I can do to help you.

Ambushed? That's the kind of question which comes up. The girl has been open and honest the OP is perpetuating a lie, which means he doesn't have communication skills and doesn't take the relationship seriously if it's taken him several weeks to think what he's done is a bad idea.