"I was dating a guy with a record and I lost everything that mattered."

There is a lot more to this story than you are mentioning. Your ex-husband was determined by the court to be the better choice as primary parent.

Regardless, your only option is to fight it through the courts.

btw: why did you divorce your husband? Were you dating that guy at the time?

Now you know how 99.9% of divorced men feel!