I'm 20 weeks and whenever I have to poop I get kind of like a pressure pain in my butt, and then when I try to poop my butt tightens up on me and I try my best to relax, the pain goes away after I poop but it's weird, I'll be asking my doctor about it tomorrow at my 20 week scan but has this happened to anybody else? It's not like I have it all the time, just when I have to poop and it's not constipation either.