Need some answers

I'm 14 weeks pregnant and I'll be 15 on Saturday. I've believe I've been experiencing Braxton hicks today and they have been on and off all day. This is my second pregnancy and I didn't really feel them with my first child. He was also born 7 weeks early and my doctor has no clue why. Anyone else having them this early?? Should I contact my doctor? They don't hurt that bad, just feels like period cramps. There's no blood or anything either.