Trying to get custody involving three states

[AWhite]

I am living in Texas and my 13 year old son has been living with me for a year. His mother,who lives in Florida, has legal custody.We both agreed that this is the best thing for him. Our divorce was done through the state of Ohio. I have a back child support from 3 years ago. She is sending me my child support back to me, but she is not paying anything to me currently. Am I going to have to go to Ohio to get custody of him and will they deduct the whole year that I have had him from my back child support. I really don't have the money to get a lawyer so I was hoping someone could give me some insight of what to expect.