Hire a good local family lawyer. It really depends on the judge. Whether or not you have been depressed is really irrelevant if it has not affected your relationship. Likewise, most family judges don't want to hear about infedility either unless it was done in front of the children, etc.
The standard for determining custody in most states is the "best interests of the child." So, that gives the judges wide subjective latitude to rule what they think is best for the child. Most states these days favor joint or shared custody orders over sole custody to one parent.
Good luck!
now that i read the thread.. she has it spot on..
if you were to see the kid, and she and her mother physically stopped you or refused, you should then go to your car, call the police, and get a cop on the spot, you might not get the child given to you, however it will prove in a court of law that you were denied access to the child, at least in that one instance..