What are my visitation rights with my kids?

I have a court ordered visitation schedule and one of my three sons is now refusing to come over to my house and his mother is encouraging his behavior. He is 16 and has lost all motivation in life. I am so worried about him. I still regularly see my other two younger sons and have a great relationship with them. I am constantly berated by my ex and her fiancé in front of the children as one of my other sons told me. He has no guidance or structure at her house and is able to do whatever he pleases. My ex and I have been in an intensive legal battle for the past ten years and she won’t let up. She continues to take me to court for needless reasons just to create chaos in me and my childrens life. She is relentless and shows no signs of stopping harassing me and now she won’t adhere to the visitation schedule. I need to do something quick as I’m very concerned about him. What are my rights?

My attorney is telling me to not pursue action and let it be. However, I’m miserable not seeing him, very worried about his future, and feel I need to pursue this. Does anyone have any advice? I’ve already spent well over 100k in legal fees fighting all these legal battles. Is this something I can easily pursue on my own? I can’t afford another 15k in legal fees. Your advice is greatly appreciated.

Thank you!