I get a sharp pain on my side when i am laying down and trying to turn over, what is it?

say i am laying on my right side, i sometimes get a sharp pain on my left when i am trying to turn over and vice versa. it is not excruciating, and goes away when i don't turn. it's like i am pulling something. i called my doc but it didn't seem like she understood what i was saying. i was wondering if anyone on here knew what i mean. the pain is irritating, but not intolerable. i am 34wks along.