I just need to vent about this..

I had sex for the first time ever with my boyfriend whom I love so much. He has had one previous sexual partner, which I would expect most guys to at least have one, but I wanted to be able to share that part with him too. He says he loves me and has never felt this way about someone, but it still hurts feeling like his ex was able to make him feel good and I am having trouble. It hurt me a lot and he had trouble going all the way in me. I told him that I would let him know if the pain was too much. However, he hates feeling like he's putting me in pain, so both other times we tried, he stopped because he lost his erection (thinking about hurting me made him lose it, then after that, he could only think about trying to keep his erection). This is frustrating for me. I feel like his ex had something I don't, and I know it is dumb, but idk how to get rid of that thought.