Defenitely sounds like it's back-related. I had similar pains for several months, prior to being pregnant, and during. There's the sciatic nerve that does down through your butt cheek, so it could be that, and there's a muscle right inside your hip bone that could be inflamed, which means it could be pressing on a nerve. Try some gentle stretches in the morning and throughout the day, whenever you feel it acting up. Your doctor could probably tell you some good ones. I went to a chiropractor for my pain, and he fixed me right up, plus I did gentle stretches and exercises. Just make sure it's a chiropractor with the special table for pregnant ladies, the middle section drops down to make room for your belly. I don't know what I would be doing now if I didn't find relief, I couldn't stand up straight most days and sitting at work was agony. The exercises will help stretch and strengthen your back muscles, might take a while, but hang in there! Feel better!