Cramping 16 weeks

Kk

Has anyone experienced cramping around 15 and 16 weeks? It isn't as strong as my period cramps normally are...but it's kind of like the cramps you might get a day or two before your period. It comes and goes....it isn't constant cramping. No bleeding whatsoever. I have a Doppler and I can hear his heartbeat, the rate is always 140's, but this cramping just worries me.