monitor not picking up comtractions

i’ve been on this monitor for about 3 hours and it is not picking up my contractions. and i just know they about to send me home. i had this same thing happen to me with a previous baby at this same hospital and i was given discharge papers and everything until i told them i needed to push and they decided to check me and there was my baby coming out. why would they monitor not be picking up my contractions. i’m in so much pain. i know what i’m feeling but they aren’t listening. omfg. yes i am a plus sized person. does that have anything to do with it? should i go to a different hospital? somebody please tell me something.