You definitely need court ordered child support. I get it's difficult raising three small kids alone, but it's possible. I know, mine were 3,4,7 when I divorced. 7,8,11 now.
If he wants to bash and claim you keep him from his kids, so he draws attention and pity, let him. It's not truth, don't make his delusions, your reality.
Life eventually moves on. Sadly, sometimes, actually more often than not, our first loves aren't our final loves.
Take the time to find out who you are, above and beyond motherhood. Don't let the loneliness and difficulty of being single and a mom, lure you to someone overly demanding and taking advantage of you. Solidify you, first. Before dating again.