30wks preg. Having abd/back cramps. OB said was having contractions. No dilation. Observed for a bit & released. Doing it again worse. What are these?

A few thoughts... It is common to have Braxton Hicks contractions during the later part of pregnancy. These typically do not result in delivery. But a urinary tract infection may spur on "real" labor - and since you are preterm, you don't want to have this happen if you can prevent it. Make sure that you are getting plenty of fluids and that you are checked for UTIs.
Contractions preterm. If your contractions are getting stronger, you need to go back to the hospital for evaluation. They may only observe and release again. That is ok. Its better than being in pre-term labor at home and not knowing it and not going in until its too late to do anything to stop them. Best wishes!