OK, well, this is a good way for a person to check where the problem is. If they have a behaviour they don't like, in almost any company, then it's something for them to look to themselves to sort out. If they have a behaviour they don't like, but it only happens with one person, then that person is the problem. It doesn't mean they are 'a problem person', it means they are a problem together, compatibility wise. And when two people aren't compatible, they need to stay away from each other or there'll be fireworks.
You're currently being responsible for your kids and your partner, but not for yourself. It's up to you to decide who to be around. It's up to you to decide who's good for you. It's up to you to choose people you feel good with.
The reason you've lost your identity is because you are not recognising you. You are not speaking your mind. You are letting your feelings be over ridden.
This is how boundaries work: you make it clear, calmly, to the other person, what you need. Then you watch and wait. If they make moves to provide what you need, you go forward with them. If they defend themselves, make excuses, minimise your feelings, make you feel silly, put you down, etc, you leave, confident that you did all you could.
If he chooses not to provide you with some time to yourself, and he chooses to leave his dirty underwear for you to wash, then he's not entitled to stay in a relationship with you, because he doesn't respect your boundaries.