Dear Happy99110~
Welcome here to The Forum. I can understand with BPD you may indeed need something to help you cope, this does not necessarily mean you have to use illicit substances. I have PSTD, and coping with the trauma, depression and anxiety has been treated with a combination of medication and therapy. This has had a long term beneficial effect, though I must admit a large range of prescription medications were tried before the right combination was found.
Any worthwhile rehab service will be under stringent medical supervision, and not blindly go ahead to try to get you off a particular substance. This can be your chance to explain what you have needed to do to cope, and hopefully they will listen and do the same as happened to me, trying various meds until an effective one or combination is found. The range of meds can be surprising.
If you lose a place to live that can only make things worse. I've no real idea why your family has laid down the law, possibly not seeing you take substances that are of an unknown strength or possibly lethal composition, maybe they do not like to see you so reliant on anything. Perhaps you have had to bend the rules to keep on buying.
So may I suggest you give rehab a try, and make sure the underlying reason and the effect of taking this dug has for you is listened to.
If you could I'd really like to know how you get on
Croix
