Pregnancy concern

I need reassurance or something. I got to the ob Monday but wanted a little advice before then. This is my second pregnancy. Ill be 16weeks Monday and haven't gained any weight like I don't look pregnant just my boobs have gotten larger. My daughter seems to stick to my left side a lot and I'm hurting sometimes in my legs but mostly in my left butt cheek half way up my lower back. I can't seem to ease the pain but I'm starting to get concerned. Has anyone else experienced this?