How can I get custody back of my children after a drug conviction?

My husband and I lost custody of our 2 children 7 years ago. He was charged with a felony possession of a firearm and sentenced to prison for 9 months. I was charged with misdemeanor endangering the welfare of a minor for basically not keeping the house the way it should be and we were doing drugs. My aunt works for DHS and she was a big part in getting my conviction and getting them put in a foster home, which I know is conflict of interest. I had a DHS worker from another county tell me I could have them back immediately because of the conflict of interest. But, beside the point, there was a lengthy custody battle in which my daughter's grandparents (not related to our son) were given permanent custody of both children. We DID NOT sign away any parental rights and were assuming it was temporary until we got our lives together and our legal issues taken care of. My husband did his time in prison--9 months--without getting to see our son at all. I was given visitation on Saturday of each week. No phone calls. When my husband got out, they allowed our son to spend the night occasionally and sometimes a week during the summer or spring break. But they always treat us badly. We both had jobs, we turned our lives around and were doing well for ourselves but nothing was ever mentioned about even remotely getting custody back. We were paying our child support every week, it didn't go through child support enforcement, it was a written agreement between us. Then, in October of last year, my husband lost his job due to severe chronic pain and degenerative arthritis and degenerative disc disease. We made a deal with them that he will pay off what we owe in child support when he gets his SS. But it is really taking a long time, so they are mad. They think I should be working 2 jobs and there is no way I can do that and take care of my husband and his grandfather. Since we are so broke and unable to pay the child support right now, they have cut our visits to every other Saturday and NO overnights at all just because we don't have any money. They are punishing us, but they are punishing our children more. They both hate it there because the custodial grandparents are very strict and in my opinion mean. Both of my children tell me how much they hate it there and how they want to live with us and how the grandparents are making their lives miserable. We don't have money to take it to court. My daughter is about to be 18 in 2 months so she is planning on moving out, but I can't stand the thought of our son having to stay there in a place he hates for any longer especially without his sister. Our hearts are breaking because we are not bad people anymore and we love the children more than we can say and we are getting cut out of their lives because we are poor. Do you think DHS could help or would we have to get a lawyer and go to court? Is it possible to find a family lawyer that does pro bono work? I just don't think that all of us should have to suffer anymore when we are not doing anything wrong...we are just poor. HELP!