Cramping at 30 weeks...

Samantha • We are expecting baby girl #2 on 10/31! Can't believe the changes coming!I work full time as a Vet Tech and live in Maine.
I am 30 weeks tomorrow and have been having on and off cramping that remind me of less intense period cramping (I usually get crippling cramps during my period). It is my lower back, abdominal area, hips and upper thighs. I was recently told I have a low lying placenta (never told me before) and I have an ultrasound to check the status of it next Monday (not tomorrow). Is the cramping something anyone would be concerned with? It's our first.