Child being molested

I have this gut feeling something is happening to my son (he’s 3) but he isn’t sharing anything with me. All of the signs are there. I too was a victim of molestation most of my life as a kid. I keep having dreams about things happening to him or my daughter but my son keeps coming up. He talks about body parts, he has played with stuffed animals in a sexual way (he closed the door to play with them in that way) and other things that I will spare the imagery. His dad and I Co parent. He dad is jealous of my new life. He was very toxic (blamed me for my child’s death/ DV etc) I have been picking up on the fact that his dad constantly distracts him from FaceTime when I call the kids. He has weaponized my kids against me and has spewed lies. My son constantly talks about his dad (for some reason I saw my dad as the good guy too) anytime I ask it feels like he’s been groomed to call me a “liar” and he insists that it’s not happening. He’s over the top angry about everything to the point of where I’ve considered therapy. I know something is happening. In one of my dreams he was letting it happen. He’s constantly distracted. He’s dad told the court he was going to put him in school but he isolates him. Constant tv and games. He’s only 3. When he’s at my house he says he has to whisper things to me bc he says his dad can hear him. He’s being manipulated. I don’t know how to get him to tell me the truth. I need proof in order to take legal action. I already told the court I wasn’t comfortable with over nights bc his dad still sleeps with my daughter and my son. They should be in their own beds. When I confronted him and shared that they needed to learn boundaries for their own bodies safety he mocked me and came up with reasons why it’s ok to sleep with my children. I need help. It took me until I was 17 to say anything and to be shown it wasn’t my fault. From his age to 17. I still deal with that as an adult. I need to help my son. I’m not sure what to do.