TMI: Painful Sexy Time

So I'm 34 weeks with twins. My SO and I decided to try having sexy time which ended in a disaster. We haven't had an issues with sexy time during this pregnancy, it's been a little over a week since we had sexy time, so we wanted to work into it. We eventually, decided to have sexy time and it was horrible. No matter what position we tried, I felt like he was going to break me. We've never had this issue before, but it seriously felt like he didn't fit and like he was hitting something. He tried to use a finger (a pinky) and I started to yell at him, because it felt like he shoved his whole hand in me, but it was only his freaking pinky. In the end of it, I started to have really bad lower stomach cramps and had to soak in the tub. I was in so much pain I couldn't stand up all of the way for a few hours and this morning I was super tender. Sorry, I know this is all TMI and I plan on talking to my doctor about it, but I was just wondering if anyone else may have had a similar issue or know what may have caused all this pain?