Pain during sex.. HELP!

I didn't know how to word the title, so excuse me for that. The last few days when my boyfriend and I have sex, I get a really sharp pain in my lower stomach area and sometimes it'll shoot up to my chest and make it hard to breath. This happened last night as well and the pain was unbearable. I don't know what to do. I don't wanna go to the doctor because I'm stouburn and don't like to go. If he puts his hand on my stomach and slowly rubs it, the pain will slowly start to go away. I need advice. I don't know what to do. Help!