contractions

So this is my first pregnancy, I'm 33 weeks today, I have cholestasis, so I am being induced at either 36 or 37 weeks. They don't want me going past 37. Anyways, in my the meantime I have to have nonstress tests done twice a week to make sure baby's activity and heart rate stay in a good spot. Well they hook you up to the monitors and then the nurse leaves and watches the activity on her screen outside the room. At my test yesterday she popped in after about 20 minutes and was like "are you doing okay?" And I told her yes and she said she wanted to check because I was having consistent contractions. When I told her I wasn't feeling them she seemed very surprised. Has anyone else gotten these and not felt anything? I've had Braxton hicks before and I felt the tightening with those, but not with these contractions.