Child Support in the state of Florida Help?

I was just wondering about something..My childs father hasnt paid child support in alomost 3 years..Iv tried contacting him about it and my parents have told him he needs to pay but he fails to. Iv tried getting lawyers involved but he moves all the time and never has a working number when we tried to contact him. I was wondering if I would take him back to court would the courts lower the amount that needs to be paid? or would they still even though its been 3 years make him pay the full amount? Im lost and dont really know what to do and I have tried everything I can and dont want the amount that he owes my son to be lowered because he refuses to pay and doesnt think he needs to pay. Help please.