Custody change?

Basically, I have joint custody of my son and his mother has physical custody. We've gone back and forth to court since he was about a year old. He's now 6 years old and and its been about 2-2 1/2 years since the last time we were in court. My issue is that I want to have the order changed from joint to either me having Full Custody or 50/50 Custody. My son and his mother were living with her mother and about 2 or 3 years ago I found out that his mother moved out with her boyfriend and left my son with her mother without me knowing. I did find out about 4 or 5 months after she moved and was told that the boyfriend's apartment was too small for both of them. Since then they have moved into another apartment, but my son still lives with her mother, his grandmother. I'm still paying child support to this day, which I give to her mother who claims that my son's mother is giving half to her mom for our son. My son's mom and I did not speak for over 2 years, everything that has to deal with my son went through her mother. If I was making any plans, insurance, medicine, visitation, etc., was always between the grandmother and me. There have also been times that was not allowed to get my son because they had plans. I want to know if I have a case based on that information. Even though I am a manager and go to school I don't have enough money to afford a attorney, if anything I really need legal advice on the situation. I will be more than glad to talk more about the situation to anyone further.

You need to find the money for an attorney. Change your life. Do without some things.