I am really sorry to hear that.
It might be upsetting to do, but have you asked her outright for help and support? Really put it on the line. Tell her you want your life back. That it’s possible for recovery and that you need some help on the road to it.
You say you’ve lost contact with your friends. Same question- have you actually said “I really need some help here, can we meet up once a week to have a coffee/ walk/something for an hour, I really need some help.” Even if you can meet up with one person and talk about anything at all, football, or films or cars or whatever you like, I think you’ll be in a better position.
Depression is isolating and that can compound the problem. A lot of the strategies here are “manly” ones - lift weights, etc. But really that sort of thing doesn’t have much impact on mental health versus a support network. I am obviously not a medical professional and don’t know how this condition contributes to mental health problems but it makes sense to me that having an extra person in your corner and taking a break from being alone will help. Creating a situation (or sleepwalking into one) where you’re all alone will not help.
It might even be worth considering a longer stay at your sister’s.