Well, it's normal if he just doesn't like it - there are all kinds of things that fall under the ranges of "normal", like some people like strawberries, but it's normal that others don't.
Is him saying it's "just not his thing" covering up for something else, like erectile dysfunction? Anxiety? Trauma?
Does he like oral sex? Does he enjoy doing things to you, like foreplay? If it's just penis-in-vagina sex, it may not be his thing, but has he ever explained why? I don't think he needs to write a 10 page paper on why, but I do think that this is important enough to warrant more than a "not my thing" if you want this to continue and it's affecting your self-esteem.
Don't accuse him of anything, and don't get angry. Just gently ask if you can have a conversation about it so you can understand and not take it personally. If it's really just not his thing, then you can make a decision about how you feel about that, and a future without intercourse. Any decision about that is also valid.
Good luck and let us know how it goes.