Me and the father of my children are trying to make things work for the sake of our kids. I do love and care for him but it’s complicated. I know he loves me too but again complicated. We are separated but he comes on the weekends to

Sounds too complicated

are you on any medication by chance?

no. Not on medication x

he’s not hesitant at all. He orgasms every single time. But not me.

I’d say you probably have something snide that you are maybe holding resentment or ill feelings towards which are preventing you from being with him 100%

does he help you orgasm before or after? because lemme tell you, if he doesn't, then I wouldn't be sleeping with him lol. I used to hate sex because I would never get to orgasm and it would just be over whenever my partner was done. my current partner makes sure that I orgasm whatever it takes and it's completely changed my view of sex. have you considered using something like a bullet or wand during sex?

You're not in it emotionally. Women are emotional beings. Men can orgasm damn near anywhere for anybody at any time.
Working it out for the sake of the kids doesn't work out. He's going over there in the weekend to spend time with his kids, sure.. But you're giving him the best part of yourself. That's all he needs. He's being fulfilled, you're not. In order to work it out, you need emotional stability. You clearly don't have it. Maybe take a step back from physical intimacy and actually work on the relationship, or throw in the towel.