It is very much like an addiction. The arrangement you are in has provided you with a measure of safety. You don't want to give that up. You don't see much in the way of options. Each day you think, "Let me just stay put right here for a bit longer. There's really nothing else I can do." The problem with that is the price you will pay down the line.

What seems like a solution for today can cause you big problems. Getting free of this man will open up other opportunities for you that you will never even know about, if you stay in the rut you're in.

You describe him as your friend, but is he really? He sounds cold. Between friends there is a degree of love. If you weren't splitting costs and providing him with sex, would he even want you around? Does your welfare matter at all to him? You say that you both have mental health and emotional issues. Beware of making false equivalences. Is he really giving you as much as he takes from you?

This is not about blaming you for anything. You are in the midst of bad circumstances. It's abnormal to not have family to lean on. It sounds like you have no one, except him. I understand you clinging to him. But what if he vanished tomorrow? Is there any kind of public/charitable agency that can place you in a shelter of some kind? Open your mind to all possibilities. What might seem like a step down might actually be the first step towards personal freedom and a chance to build what is rght for you. Life is not kind to those who give up and settle. Doing what is hard now could save you a lot of future grief.