I had it too, it's pelvic pain and my doctor said it was a normal pregnancy pain :)
I get this too! Im 32 weeks and just the othrr day I lifted my leg and my partner thought I was in labour, the shock of the pain was ridiculous I only get the pain for a second but it really hurts! Im gonna ask my midwife next time I see her
Maybe sciatica? Call your dr just in case. Good luck.