Can I recant after someone has already been incarcerated and how do I prove a wrongful charge or sentencing?

My son father is incarcerated. I testified as a character witness but of course our relationship ended up on trial. I have been trying to get visitation for me and our five year old son. They did DNA on my son last year and proven paternity. But his PS records still states he does not have children. According to his counselor at the prison his PS record have me as the victim. He was on trial for armed robbery nothing to do with me. He was also charged with intent to do great bodily harm less degree then murder. As a character witness, I did not do well. I was angry at him on so many levels beyond stressed but more hurt that we were not on the best terms when he turned himself in. He was not alone when he committed the crime but the other guy didn't get caught till a year later and he was only charged with robbery. I was furious that he was involved in the circumstances for I didn't know or think he would be caught in this situation. Our son was only eight months and I wouldn't have dreamed of him getting twenty three years. My intent on the stand was to make sure the jury understood that he was state diagnosed retarded. He was bipolar and he had childlike behavior. He had just turned twenty one and there's a huge age difference between us. I really didn't know what happened only what he told me and I now realize I should not have been on that stand. He cannot read and have comprehension impaired. I know he was railroaded and hate that I play a part. I was a heavy marijuana user at the time with two kids, one special needs and I just needed a break and some peace. I asked him to just tell the truth but he didn't want to be called a snitch after that I walked away with angry and confusion feeling overwhelmed and tired of trying to explain right and wrong to him. I still care about him deeply. I believe you do the crime you do the time but knowing if he would have taken the deal he would only have gotten years not twenty three.