Who can help me &my husband have a voice to show that my husband is innocent...WHY IS A INNOCENT MAN IN PRISON?

My husband was accused of ual ault on a child by a pissed off ex-girlfriend with an axe to grind. The saying is true..HELL HAVE NO FURY LIKE A WOMEN SCORNED.. We have evidence to prove that the accuser was making it up and she was just mad because my husband left her. 3 months after leaving from living with her( for 2 months) she files these charges. We have a witness that will testify to the fact that the accuser told her 3 months before she filed the charges that she "would do whatever I could to put him back in prison." He has a prior charge and he served prison time when he was 18 and she(the accuser) was his girlfriend at that time(the DA didn't know that). His prior was him taking a rap in order to make his "homeboys" proud and they would all be there for him when he got out.A stupid choice when he was 18. The accuser knew this and still stayed with him during his 3 yrs he did. She used that knowledge to put him in prison for a crime that he didn't commit just because she was mad because he didn't want to be with her again. How in the world as an American Citizen can an innocent man be sent to prison for a crime that he didn't commit!!!! There was no evidence against him, including no physical evidence even after an examination was done on the child. There was no signs of anything and according to their story if it would have happened there would have been signs of something. but he was scared into taking a plea deal. They used his past against him and told him that if he went to trial and was found guilty for any reason it was an automatic life sentence. Or he could take the plead deal of 10 yrs probation up to 18yrs. He wasn't even given the chance to show what he has to prove that he is innocent. He was just forced to pick a gamble with life in prison or 10 yrs probation up to 18 yrs prison time. And it was a hard decision for him to make because he always said he would not take any plea deal because he is innocent, but he was almost guaranteed the probation even up to moments before he was sentenced to 18 yrs the lawyer was explaining what he was gonna have to do while on probation and now he is in prison serving 18 yrs :( PLEASE, PLEASE CAN ANYONE HELP US. OR DOES ANYONE HAVE ANY IDEAS. OUR DAUGHTER MISSES HER DAD AND I MISS MY HUSBAND!!! THANK YOU