I signed over my rights to my child, due to a ongoing cps case, I signed him over to the natural father, we had made an areement that as soon as cps case was closed ihe would sign him over, well cps case closed and he doesn't want to give him back! what can I do?

Are you saying that you signed away your rights or just signed full custody to him?
If you signed total rights completely over to him (terminated) then he tricked you into it by making that agreement that would never even hold up in court. Since CPS was involved because of an ongoing case I assume that that is what you did do.

If he filed for full custody and you did not sign away rights or if CPS did not take away your rights then you can possibly go to court and file for joint custody with visitations.

Sounds to me like you were led to believe something so that he would have them with no recourse though.
Also if you made that agreement it was fraud and wouldn't work out anyway. There is no way he could just sign them back without the court that took away your rights in the first place being involved.

If your rights were terminated, a judge would have had to sign off on this, then you can't get him back. If the father just has custody and your rights haven't been terminated then you have to go to court to file for joint custody but I don't know of a judge that would just switch it back to you having full custody and the father with nothing if that is the case the best you could hope for is joint.

Courts are reluctant to grant Terminations of Parental Rights. So, if one was granted by a court in your case, then its highly unlikley it will be over turned. What EXACTLY did you sign? What were the circumstances? Did you appear in court?