How do I tell him I don't want to be in a relationship and stay how we are?

Tell him you want to keep him as a friend with benefits for the time being and don't forget to tell him to stay single until the day you realise relationships are not that bad and that you probably won't do any better.

Thanks for replying!
I don't know how serious you are with this response, but I'm going to assume you don't mean to come across as patronising as you did
I don't really like the term "friends with benefits", and I wouldn't mind just friends, but I assume he would prefer to have a sexual side to it, since being "friendzoned" is something a lot of guys seem to fear, and I'm not opposed to the idea, either.
And I'm not being short sighted, I know that relationships and me don't mix and I think it's wiser of me to not attempt them instead of having it result in a disastrous relationship. Maybe I will want one in the future, but I'm mature enough, I think, to know what i want and don't want.

You don't want to enter a relationship incase it ****s up?

Comeon... You're missing out on a lot with that attitude. It can't possibly be that bad. I know... You have a mental problem with relationships, but the only way to solve that is to try and develop a decent one and why not try and do that with this guy if he's so into you; you enjoy the sex; and you somewhat enjoy chatting with him?

At least if it's all just uber-horrible then you know "**** this doesn't work for me" and can just call it quits on the relationship thing. But you haven't even properly tried it yet?

Well, I get where you're coming from, but I have to disagree. The logic isn't very good, it's like telling someone that hates cats that they should just try owning one, maybe it's not so bad, or someone who says they aren't attracted to men to give it a try. Pretty abstract examples, but hopefully you understand?

I probably will at some point want a relationship, and to be honest I do think I have some sort of commitment issue, but forcing myself into a relationship isn't going to solve them, I don't think. I'd rather wait until I really want one. I don't regret my decisions so far, so it's not like what I'm doing is hurting myself, I am very happy with my life as a single person.

Plus, getting into a relationship involves two people, so if I were to realise just how awful it was afterwards, it wouldn't just be me that experiences whatever negative emotions follow.

I appreciate your input, though, and I see where you're coming from :-D

If you'e never seen a cat or seen a man in real life and only heard about then yet nonetheless have a phobia/anxiety about them, then yes, I would tell you to set up a controlled environment that you can escape from incase it goes haywire and try it out nonetheless. I used to be scared of dogs really bad when I was young but every year we went up to Scotland and slept in my aunts house in which there were three dogs. As you can imagine at first I was ****ing terrified - immobilised with fear and constantly paranoid. But eventually I realised, actually, these beasts are cool. They are empathetic generally well-intentioned to people who aren't dicks to them and have very predictable behaviour and are super cute. Now I have a dog of my own. Obviously sexuality is different as it is not an anxiety. However, I do believe a lot of asexuals and aromantics are not innately so, rather it is a manifestation of a particular or a set of anxieties that they have with sex/romance. So I'm not sure your analogies work.

The best way to overcome any irrational anxiety/fear is to face it. Ridiculously hard I know; you need to set-up the right scenario for that to happen, but how else will you ever do it? It's awkward because right now you obviously don't see the value in ever pursuing romance anyway so you will have little motivation to get rid of that anxiety... But if only.

Yes... Inevitably if it fails you'll hurt him. But, you're going to hurt him anyway rejecting him on the basis of you not wanting romance. He'll likely just think he's not good enough for you and then it will be even worse if you keep having sex with him because he'll think you're just using him and start to resent you and probably feel bad about what he did with you in the past. Maybe... I don't know, that's how I'de feel anyway. Some people are fine going around with 4 FWBs simultaneously though... But from his texts it doesn't seem like he is, right?

At least if you give a go and it fails he'll see that it just won't work and he'll be able to accept that and move on without being distraught.