What Causes Frequent Urination And Stomach Pain?

Me and my fiancé have been having unprotected sex for months now. I had my period last month, but its not time for it yet this month. But I'm scared, I could be pregnant. I was constipated for weeks, and its still hard to go. I've been peeing aloy more than usual. I've been eating more too. My stomach has been hurting a lot, and the other night my stomach hurt so bad. It started from the top and seemed like the pain starting going lower and lower. I couldnt tell whether I had to poop or puke. Which I dod neither. My eyelids seem to stay heavy. Help?