it doesn't matter at all how many lays you've had, but if you like your boy then you have to accept him with all his human frailties, and this is one of them.
Speaking as a man, I know it doesn't matter, and I know that the fact you've had a lot of men doesn't matter, but if I was your bf, it would still bother me. And knowing that it doesn't really matter and I'm being silly wouldn't help at all, it would still bother me.
So the first thing you have to do is accept that it probably will bother your boy, and the rights and wrongs are basically irrelevant.
Now if you can accept that it will probably bother him, you can look at the why and the how.
I've been in his situation before (actually a few times, a few years ago - now it's mostly the other way round) and there were a few reasons it'd bother me. Please excuse me for speaking rather frankly:
-I'd be afraid you're a bit of a **** and are going to cheat on me. Can you stop sleeping around? Are you going to shag someone to make yourself feel better after our first fight?
-You have so much experience, are you going to judge me in comparison to those 20 guys? There must have been some with 10 inch appendages who kept going all night and made you come every time. What will you think of me when I can't compare?
-this is the harshest bit, but it's true. Deep down, we basically have a feeling that women who've shagged a lot of men are basically just a bit dirty. We think virgins are pure and clean and lovely and we happily go down on them, but if you've had a lot of sex, it just feels different.
Right, that's the why. It's not nice, but it's fact. Everyone's different, but I suspect your boy will basically be feeling something like what I've outlined above. You don't have to like this, but you cannot change it. You also can't talk him out of it, or persuade him not to feel that way. He feels that way because he's a man and that's the way we are. He probably knows it's silly, but that makes no difference. All this stuff is basically hard-wired in our Dna. Women might not like it, but it's part of being a man.
What to do?
First things first, my advice is don't address the issues head-on. He might nod and say he agrees, but he won't change inside. You can say 'it doesn't matter', but Don't go in-depth. Also DON'T expect him to acknowledge the fears I've outlined above, that would be rather humiliating.
Firstly, it was a little bit silly to tell him in the first place. I suspect most girls lie about this because they know their partners want them to be less experienced.
Of all my more-experienced women, the one who handled it the best was the on who never told me. She just avoided the subject and said it didn't matter, and because she didn't act like a slut, I just forgot about it.
Unfortunately you've already told him, I think. So here's what I think you need to do.
You need to look at what he's afraid of, and counter those fears. You don't have to do all of these things if they're too burdensome, but it's up to you.
-He thinks you might be a bit of a **** who'll cheat on him so: Never cheat! Don't flirt with other guys in front of him. Call him when you're out drunk, so he knows you're thinking of him and not humping someone else.
-He thinks he might not compare in the sack, so: tell him he's great. Pretend he's big! Tell him you don't usually come. Don't tell him, all the things you've done. If he wants to try new positions / toys etc, be coy and say you'd like to try, but don't tell him if you've done it all before. Let him take the lead.
-The virgin question: this one's probably the toughest: don't mention your previous experience. If he asks, avoid the subject and say it doesn't matter, if he presses you, make sure you tailor your experiences to sound like they're a thing of the past, and avoid going into the gory details. If you have to, talk about how crap all those guys were. But not physically crap, don't say they were too small or something, say they were boring or didn't treat you right. Never, never introduce him to any exes, especially good looking ones. Best not let him see too many photos either.
That's all from me, you don't really have a big problem, but my advice I'd that if you like this guy, accept him as he is. Don't try to change him, because you can't. Just try to alter the way he sees you and your past.