Ex husband is not paying child support.?

Florida Court ordered he gets child custody every other weekend. He paid the first 2 months of child support starting 9/10 and hasn't paid since. Its now 6/11. He gets paid military disability after getting kicked out for doing drugs. I'm going to quote the judge. " I don't want to hear about you drinking or doing any drugs on the weekends, do you hear me ". When my child starts going to school he is to get custody for 2 weeks during the summer something I would have to sign by 4/15. He gave me a typed up paper he typed himself to sign on 4/22 for this week that he would have my daughter for 2 weeks straight and i refused to sign it because she is not in school yet, 4 years old, and she is in a daycare program (government assistance) where if she misses 3 days out of the month I will lose the assistance and will have to pay in full. Right now I am on my way to pick up my daughter and he's refusing to give me back my daughter. He's threatening me that he is going to call the sheriff. Any advice please. Someone must of gone through something like this.