I think maybe we aren’t grasping the situation.  You are perhaps not really "with" this woman now and are questioning paternity because you have to pay child support?  Even if you are still involved with her, if you question the paternity, and it would matter very much to you, get the paternity test.  Anyone who watches daytime TV as I do about once every six months when I’m on vacation has seen the shows where so many kids end up not being their "father’s" child so you should put your mind to rest.  The CAH thing has nothing to do with it - it doesn’t indicate that you are or are not the father.  My niece has a very obvious genetic disease that the family would have definitely noticed but no one else has ever had it.  Her mother is obviously a carrier and just happened to marry another carrier.

And if you’re not the child’ father, but still want to be involved and be a father to him that would be great too.