BF can you drive to Social Services? Are you functional enough to drive? If you are I would go out there and see about talking to someone personally even if it means waiting for awhile. Try to stay calm, I take avitan for my anxiety and am grateful it works. It sounds like your sister is burnt out as a caregiver even if she's not living with you taking physical care of you.
I don't know why she's doing this, maybe it's her way of giving you tough love, to try to help you, though she probably can't see how frightened you are of becoming completely unable to care for yourself like having no financial resources to do so would leave you. Has she talked about what your options are? If so what has she been saying?
Do you have Medicaid and SSI at least? I would try to get on SSI and definitely see about medcaid and food stamps. Also start looking into the local food banks in your area, get signed up, you need all the help you can get when the money runs out and for right now you need it to stretch for as long as you possibly can.
These are serious problems, but you CAN do it if you can focus on the goals you make and do the footwork to make them happen. You can get food and clothing from local 'charities' and the social workers should be able to help you. Oh boy, I was assuming you are in the US...If you're not I don't know what to tell you as far as advice on dealing with these things.
Tell me if you're in the states and have a car and maybe I can offer more advice, if not I will have to talk to some friends in the UK if you're there. Bless your heart BF, you don't deserve what you're getting tossed around at you.
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