Getting served papers

Yesterday I got served papers from my baby daddy about full custody over our son and when I talked to him he said he didn’t do it. Cps had gotten called on mee a couple months after mee and my baby daddy broke up so he tried to say that cps made him file these papers and everything. I don’t know what to believe cuz we where doing good with coparenting and everything. He said he didn’t want to take my son from mee or anything like that and I don’t want to take my son from his dad either but like with cos being involved it’s hard for us to do everything the way we have been doing. Has anybody else gone through this or a similar situation? I really need help and the papers also said something about a temporary restraining order on mee what does that mean?