Contractions

I'm 3 1/2 dilated and I been having painful contractions alot.. so I went to l&d to have them monitored... they completely stopped and when I had a few they didn't hurt really so they sent me home and said when they are more consistent that I'm having them for sure but not close together .. so once again last night and today I'm having them close together and some very painful. Some even 5 min apart for a period of time then they go to like maybe 20 apart at the most!