Yours is always a difficult situation especially since the law often makes it harder. It is compounded if your mother is unwilling to help or is deceased. If you were adopted out it gets even harder. Check with your relatives including your mother's aunts, uncles and even cousins. Sometimes they know stuff through family rumors. Also small clues about your father can be helpful, where he lived, occupation, was he in the service, if he had siblings, wife's name, middle name, approximate age, if he paid support, etc.
Since it is not a very common name and he lived in the Pittsburgh area you could try to find a marriage record for Charles. He might have gotten the marriage license at the Allegheny County Register of Wills. I doubt there were that many Charles Hintons of the right age in that area. Anyway it could be a place to start.
What does your birth certificate have on it about him? Do you have a copy of the original?