Cramping at 17 weeks

Anyone else cramping? It feels like menstral cramps. And they feel like they get more intense sometimes. Told my doctor, and she's not worried. But it just seems off sometimes :/ This is my 3rd and my second I had the round ligament pain... But this feels nothing like that. Anyone else experiencing this? It hits my lower abdomen and lower back... Feels line a small contraction almost- my stomached gets tight and then will relax after a bit.