Butt pains... Owie!

Talk to me about sciatica if you have experienced it! I dont think that is what I have since I don't feel the pain down my leg like I have heard sciatica described. I definitely feel it right in my left butt cheek, but only there. It feels like a sharp pain and usually comes when I try to stretch, but sometimes just randomly. Has anyone had this? Do you think a massage would help at all? Obviously trying to stretch it just makes it worse. I am planning on telling my Dr about it at my appt next week for sure. I am 26 weeks along and never had this with my first pregnancy.