My son came to my room while I was asleep, lifted up the sheets and saw my butt

I woke up because he and my youngest were giggling and whispering. They laughed about it for twenty minutes that they saw my butt because they think that's funny. Dropped them off this afternoon. Got a call from my ex-wife saying my oldest said he saw my butt and she doesn't want my boys staying at my place anymore on visitation because she fears the boys aren't safe around me any longer.

What the frick do I do right now? Is there preemptive legal action I should take to better place myself in a court situation with her about this? During the divorce, she said I hit them and then dropped it all after very basic questioning. My son told me and my parents that she told him that I "used to hurt him."

She tells the boys their last name is what her new last name is. She says to call her husband dad, daddy and father. She's trying to completely eliminate me from their life. What the frick do I do? I'm not made of money. I just miss my sons. She already moved 3 hours away during the divorce, which seemed fine to everyone in the court room except for me that day. What the frick do I do? I have a few texts here and there from certain times and holidays when I can't get her to let me talk to the boys.