that exactly what I had with my daughter and I was in perterm labour but the hospital didn't believe me thy sent me home and within 30 mins my water broke and I was back and there was nothing thy could do to stop it. But the 30 mins was after 7 hours of being at the hospital and 8 hours of being at home thinking if I should go in, If I was you I would be going in
I've had the exact same things and was told to get looked at if it persisted or got worse because it can be preterm labour. I think since you already tested positive you should call and ask their advice. If it is labour, they might be able to stop it.
You should call your doctor, because in preterm labor, with what you describe, it could go either way. I was in preterm labor for five weeks and had back cramps and back aches and pubic bone pressure the entire time, but never made any progress thanks to bed rest and preterm meds. However, it's hard to tell unless you are checked if you're making any labor progress like dilation and effacement, and with preterm labor, it can happen anytime. The longer you're able to stay pregnant, the better it is for the baby's development, so it certainly can't hurt to make the phone call and see what the doctor has to say about it. As you said, you don't want anything dramatic to happen if you're unaware, especially with a preemie.