I need advice

I need help guys, my sons (3 year old ) mother has started to demand what days I see my son and won’t answer the phone or the front door on days when I have him. She has become spiteful and uses my son against me in arguments, threatening to stop me seeing him. This all started because I got a new job and she doesn’t want to watch my son while I’m at work she’d rather go out with her friends and leave the kid with her mother. Her mum has now gotten a job and can’t watch him for her so she has decided that I’m not allowed to get a job because I have to have the kid because she doesn’t want him. So do I get my new job and move on with my life and try see my son on the weekends or do I do what she wants.