Filed for taxes and now he refuses to help out?

We have a 4 year old I allowed his father to file for taxes when our son was a year old this is now my second year filing for taxes and I do not share that money with his father. It’s all in a savings account, we are not together and ever since I started doing that he refuses to help me out money wise. Seriously even $100 a month would help! I don’t ever ask him for money and if I do probably every other month. He watches our son twice a week and I believe he has it the easy way because he never has to spend money on our child or ever has to watch him. I’m starting to think maybe I should give him half but I honestly believe he doesn’t deserve it.