Its a curious guy here. i just happen to have time with my girlfriend recently at our houses. however when we tried to have sex, i realize that i could not penetrate into her. I could not even insert it into her. In the end, my penis look kinda swollen and pain was experienced. Is there a problem? I have also realized that the look of my penis is kinda different from those that i came across from videos, i do not have the swollen cap that others have.

I really hope to understand what is going on as both my partner and me did not experience sex before as we are virgins.
Please do answer or help.. Thank you so much : )