Google is your friend. That should take you to whomever handles Child Support and paternity in your state. You can then contact them to open a case. You may also need a lawyer. If you've co-habitated, custody and visitation are sometimes treated like a divorce. If you weren't living together, then mom almost always has sole legal/physical custody from birth.
Re: laws in ca?
That's a pretty vague question. Have you tried Googling?