Why am I feeling like this?

I’m 15 years old and my bf is turning 17 at the end of this month. He’s had sex with 4 other girls and I was a virgin until a month ago. I gave him my virginity. The first time we did it I stopped because it was to much for me. The second time we did it though we did it for 3 almost 4 hours and it was amazing. But the last couple of times we’ve done it I don’t really feel anything. Like I feel pressure at first and then I do not feel a thing. Like nothing is like omg I love this or omg I hate this. I feel like there’s something wrong with me because I don’t feel anything from it. I haven’t told my bf because that would crush him and I don’t want him to think it has anything to do with him because it doesn’t. So does anyone have any answers to why this is happening?