Not sure how I feel about my girlfriend anymore

So me and my gf have known each other for less than a year and have been dating for about four months now. Everything was fine at first but recently I find myself a little uncomfortable with certain aspects of the relationship. My girlfriend's always been really physical, she likes hugging and kissing and holding hands and stuff which I'm also fine with but not as much as her. It's hard to explain but I guess I'm just less of a physical person than her. I also find myself not really comfortable with the idea of anything more intimate than what we have now, which she really wants. Kissing is fine but I'm not really into the idea of sex and I don't know why. I don't think I'm asexual or anything (I've definitely felt sexual attraction before) but idk, something about the idea of it just makes me uncomfortable. Is there something wrong with me? What should I do?