Support Arrears: Medicaid and Child Support

My question involves child support in the State of: Nebraska

I moved to Nebraska in 2007 from California and just recently I went back to California to visit. I stopped by my grandmothers house and was going through paper work that was sent there in my name because I used to live there. I came across a letter that was sent to me from the Superior court of California claiming I had a hearing for a child support matter then another one dated 5/2011 saying "This notice is to let you know about your right to have your child support order looked over to see if it can be changed.

I had a girlfriend that got pregnant back in 2005 and I lived with her till 2006 , we parted ways and she moved to mexico and took my son . She recently moved back and I have not been able to contact her but based on info from friends of both of us says she has not wanted or tried for child support from me because she doesn't want to go through the hassle with me. She currently gets SSi and has the baby on medicaid could this be the reason for the child support papers?

I know I shoudl call Monday to find out but here is what is worrying me , Could it be I was supposed to be paying child support for the last 4 years and be behind? I have been working at the same place the 4 years and checked my credit report its till in perfect standing. Do you think I can just add my son to my Health insurance and it should be fine?