Tmi sex question. Help please!!!!!

So every time I have sex with my boyfriend, I finish, then he finishes. We have a good time with it. However, it hurts. I've noticed that the inside part swells and then it hurts, feels like I cut myself then out alcohol on it. I get really into it so the lubrication isn't an issue I know for sure. So what can it be? We're both negative for STDs, clean as a whistle. I'm currently sitting on the toilet waiting for the pain to go away so I can go to sleep. I'm also 26w5d pregnant. Any help please!!!!