Does magnesium stop contractions?

My contractions began 2 days ago but am not progressing. They are 3 minutes apart but am only 1 cm dilated. Doctors think maybe am not progressing because contractions ain't strong enough. But i just remembered today that they put me on magnesium at the beginning of the 3rd trimester to prevent contractions and preterm labour. So I have been swallowing these supplements every single day till yesterday. My doctor must have forgotten that they tolde to take magnesium because she didn't mention it. Could this be the reason am not dilating? Also does magnesium affect milk production? I have never leaked colostrum and now am scared I am stopping magnesium today but it could be too late since am already getting contractions.