On friday, my girlfriend and I had sex for the first time. It wasn't my first time, but it was for her. It didn't exactly go very smoothly, apparently she thinks I am too big for her. I wasn't able to even get it all the way in before she would stop me, saying that the pain was too much. We eventually had to stop trying since she was in too much pain, and she said that there was some bleeding. She's a virgin (or was...) but she's explained that this is not a hymen issue, and that it's just TOO tight. Is this problem common? If we keep trying, will it eventually improve?