She is refusing my right to see the children

Let’s see if I can make this short…
I currently have joint custody and my EX has physical custody for about 2 years now. She has done everything in her power to disrupt my visitation and she really doesn’t comply with the court order. She does not allow me first right of refusal when she is performing in night clubs on school nights, she talks negatively about me in front of the children, etc. So about 12 months ago things got worse. She would interrupt my visitation schedule by calling and getting the children upset when they are with me. Trying to coerce them and make them feel guilty for wanting to be with me. She called the police to my home to do a welfare check on the children because she got mad at me for hanging up on her and refusing to talk to her while she was being irate and belittling me over the phone. I tried to pick the kids up on my scheduled day (but 45 minutes early) from school. She told the school not to let the children leave early with me. The kids were stressed out and crying because they were in the middle of everything. Well at that point I did not want my children to suffer any longer so I let her know I would not be picking them up from school. I did not physically get them for about 10 months to avoid issues but I would go see them at school during lunch. The kids would ask to see me and she would send me an email to tell me to not ask for them. After requesting to see the children I get a letter in the mail where she has hired a lawyer and is taking me to court to get full custody, higher child support, and for me to pay her lawyer fees. She states that I basically abandoned to children. After getting the letter she has refused me to see the children multiple times even though the custody order is still in place only stating it is not a good week. My question is when I ask for the children again on my scheduled week, and she refuses, what should I do?

That is a difficult situation. At this point the best thing you can do is hire a lawyer and fight this in court.