I've had SEVERE period and back pains with 2 pregnancies...my son and daughter. Both made it to term and are extremely healthy, so don't worry about that. Some magnesium (Natural Calm) really helps the bad cramps to go away in my experience, mellows them out.
in fact this pregnancy I'm not having hardly any period type cramping or back pain, which I find more unnerving, personally...just heard a strong heartbeat though, so I guess everything is fine.
Remember every pregnancy is different!