Procardia and diarrhea

Emily
Yuk...I know...but...
I am ALWAYS constipated...like have a solid bm maybe 2-3 times a week most of the time. And pregnancy has generally slowed things down even more. 
BUT I've been on procardia for preterm labor for 2 weeks now and have had diarrhea every day for two weeks except for one day. Yesterday I had it 4 times and today already 2 times. 
The procardia has slowed the strength of the contractions so I am not dilating further, but I still contract every 3-5 minutes for a few hours every day. I'm dilated to a 2 and 70% effaced. 
Is this diarrhea from the procardia or is my crazy uterus also aggravating my colon. What are your thoughts?