So much to do not enough hours in the day

Hi everyone, needing to write down some of my feels. My bd and I split when I was pregnant with my youngest and we have such a rollercoaster of a co parenting relationship at the beginning with it being on and off to him deciding he didn't wanna be with us full time that it was too much for him too be around 3/4 days a week. He's pretty flaky so it didn't come as a surprise he would leave, this affects my oldest quite alot with her saying she hates him alot refuses to go on Sundays and just does everything she can to stall. I'm currently at college fulltime and on a work placement trying to do everything and I really do take my hat off to single parents cause i feel i really struggle most of the time im so drained and i just always resent my ex for being no help. He used to take my youngest on a Monday and Tuesday but because I was late he decided he would stop watching him, as he called it babysitting him and doing me the favour. He was mad that I was late and that ruined his plan to go out. I just want a bit of a break now and then and not never happens even on his day with the kids I'm getting messages constantly asking when I'll be back to get them and how long I'll be.. How does everyone manage all this cause at the moment I'm drowning xxx