Depends on the kids really. My first 2 were normally challenging, normal struggles, up and downs, but mainly ups. Loved all the half terms with them, pleasure to take them out in the main, it was mostly good and life was good.
3rd child is so different. Milestones not reached, speech delay, sensory issues, haven't slept for 5 years (really haven't), tantrums are daily and last for hours. You can't take him out, his meltdowns in public are so bad. I feel like the worlds shittiest mother. He is learning, sort of, but it's slow going. The bickering between him ad siblings is relentless. He scratches, bites, pinches, spits, and we do all the discipline techniques we did with others and they worked, start charts, time out step, read books on what to do....
He will get there, but it's exhausting. I feel a failure most days now, rather than such a happy mum I used to be.
However, I do have a DH who pulls his equal weight. God, I'd go under if it wasn't for him. DS2 is so challenging we have to tag team to give the other one a break.
I still don't have any regrets. DS2 can be a little bugger, but he's my little bugger 
Your DH needs to step up. You are a single parent, no wonder you've had enough 