In my divorce decree it says my ex has to watch the kids when I work. I just got a new job and I have to work the weekends. Does he still have to watch the kids? Also he has not done some of the stuff in the divorce decree. How do I enforce that? Is he in contempt by not doing what he was suppose to do? We have been divorced since February he should have had time to do it.

If there is a change in circumstance, you may have to go to court for a modification of the decree. You will also have to go to court to enforce the terms of the decree.

If your hours have changed, he may either do what it says, or he may take you back to court to revise the order. Also you have to take him back to court to try and enforce the order

I agree, if your hours or job have changed since the papers were signed, you will need to go back to court and change the orders. If he isn't following the court orders, you would need to notify the court and let them deal with him.
Be prepared for him to deny watching the kids because its now during the weekend, he may be given that option.