My ex is refusing to return our kids to me after Korea citing my PTSD from MST in 2010. Any advice or experience requesting a custody trial?

Was assaulted in 2010 while deployed to Iraq. Upon my return had custody of the children. Court order was modified in 2014 stating my ex would have custody if I was deployed. Caveat he had to return them to me within 10 days of my redeployment stateside. I deployed to Korea October 2014 and I returned December 2015. Custody order was in my favor to receive the children back however ex-husband refused to give the children back to me and refused all visitation. He is citing my PTSD from the MST stating that I am unfit. I have just recently retired honorably with a 50% rating for PTSD both Army and VA. Buy legal light rights I should have the children however I now have to go through this custody battle to get them back. I am curious if anyone has gone through this has heard of anyone going through this or has any opinion on this subject. Thank you.