If you mean that the father of your baby owes you child support arrears or has arrearages, then "NO" you WILL NOT loose that money. Child support is a court ordered debt and he is legally obligated to pay that amount. This is regardless if you marry him or not. Even if or when you marry him, an on-going child support order will remain in effect until you go to court and have the order terminated or suspended. It is quite typical for a husband or wife to pay child support. The circumstance is only whether there is an absent parent(s) in the child's life or not. If you want to voluntarily give up that money...you typically can do so, but the number of times may be limited to just once. You may want to find out if you can leave the money "on the books" or in the system and just request to have the amount not collected. I've seen this done, as well.
Additionally, if you or the child have ever been on public assistance/ welfare, that money may be owed to the state. In this instance, he owes that money and will have to pay it back eventually. Plain and simple...he was ordered to pay...only you can forgive a debt that is owed to you...it cannot be just taken away.