My wife and I were doing it and she told me that I hurt her while was in her. I’m just average and wasn’t sure why I hurt her. We have done it many times since we met. I feel really bad and now I’m afraid to enter her and hurt her again she’s not mad at me it just bothers me and feel terrible about it.
I don't know what's causing it, but don't assume it was you. Maybe she should see a gyno. She might have a health issue that she isn't aware of like an infection. Whatever you do, make sure to address it soon. What you don't want to happen is to let it linger. You might get used to not having sex and have other thoughts about lack of intimacy creep in.