What to expect if my ex husband is not paying child support?

I have been divorced for 1 year and separated for almost 3. My ex husband and I both signed the divorce agreement and he is not following it. We have twins and he is suppose to pay 270/wkly to DOR and he is always behind. He never can just send them the check every week. I already filed a contempt last year for non payment and they intercepted his tax refund. Well here we are again. Now he is almost 5 weeks behind and he never believes the amount he owes. Or always has an excuse with his checks not getting there. We also have agreement that he has the kids every other weekend and 2 weeks a year. The two weeks have to be confer and established by December 30th if he takes them on their school vacations, or by April 30th if he wants to take them for their summer vacation. Here we are June 6th and cannot get a schedule from him. I have tried to set that up with him on several occasions and he is impossible to deal with. So I went to the court house and filed 2 contempt for the visitations and for the arrears he owes. I filed and brought the paperwork to the DOR office and they said that they would take care of the DOR contempt and I would have to take care of the visitation contempt. After filing at the court they took the paperwork and that was it. I thought I was suppose to have it served to him from a sheriff or constable. I just don't know what to expect and how long it should take for him to get served. Does anyone have this experience or similar that can give me advice? Or if I am doing the right thing, or if there is something else I need to do. Thanks so much in advanced.