Children being withheld from parent

I’m a single father and face this situation a few times a year. My ex-wife will withhold the children from me when its my scheduled time to have them based on a variety of circumstances such as ….1. She made other plans with them and didn’t tell me or she gets upset at something i disagreed on and withholds them from me. I made a model that I need help with.

C- Mother withholding children from seeing their father
T- She’s hurting the children by withholding their parent
F- Angry
A- I see the kids less, I speak to them less,
R- I have less relationship with my children.

I’m not really sure how to change my thought on a circumstance like this. Is it something that I should seek court help with since she’s abusing her control over the children? I’m afraid of the court giving me less time with them. I’m afraid of them charging me 4x the child support. I feel a little helpless in this circumstance. Things are out of my control and it brings me much sadness and anxiety. I worry for my childrens future and I’m growing more resentful from her actions.