17 weeks with semi urgent question

Priscilla
Hey y'all. Question!
17 weeks today with CPP(complete placenta Previa)  (diagnosed at 14 weeks) I know back cramps are normal and all, but when is it appropriate to go to the hospital. The hospital I will deliver at will send me to L&D since I'm past 16 weeks. 
I've been having horrible back cramps that feel like a period, and some cramping in the front. No bleeding or watery discharge. S/O just gave me some Tylenol, back massage and I stretched. But it seems to get intense. 
Anything will be helpful. Much love to all of you ladies.