I'm in a committed relationship and all of a sudden?

If you are so against it - then don't do it. Wouldn't be fair to him, the children. Or you.

You will just become more resentful and will, somehow, take it out on him and the children.

So move out. Tell him you are willing to still see him. But you don't want to take care of a family any more.

It's neither right nor wrong - how you feel. It is what it is.

You should never have moved in with a man with children with these strong feelings. It is your life. But try to make the transition easy for him due to the huge stress he will have being a single father all of a sudden.

This is a disaster waiting to happen. You need to move out ASAP and limit any visits that include his kids. You will now be second fiddle to the kids so you need to either accept that or move on and frankly, you'd be better off moving on to someone single.

Find someone else & be that guy's mistress then. Kids will always come first and he will always have things going on with them and they WILL take priority over you.

you raised your kids and you are done, just be honest with him, you have the right to walk. Better to be honest and go your separate ways than to stick it out and be miserable