The point is that you said you can’t leave, and asserting and holding your boundaries is how you get the space you need. You probably will feel bad initially, but you’ll adapt. You’re an adult. You’ll learn to deal with the discomfort.
However, if what you’re really saying is that you do want to leave, which would be completely understandable, then that’s a different conversation. Start a thread about it, ask for advice on your specific situation, and people will point you towards resources that can help you, as Mumsnet says, get your ducks in a row and leave.
Right now, it sounds like you’re spiralling, upset, and not actually moving forward. You need to decide. Option A: you’re staying, in which case you assert yourself, hold your boundaries, and carve out your space as a human being. Option B: you’re leaving, and you start taking practical steps such as financial, logistical, or emotional preparation so that you can do it safely and on your own timeline.
Until you make that decision and act on it, you’ll stay stuck exactly where you are. And that’s not what you want.