I understand that some surgeries, have places where if people feel the need to cut, then they can cut safely.
Personally, I would try to devise a 'keeping yourself safe plan', so that if you do feel the need to hurt yourself you can tell a supportive, non-judgemental person, perhaps a worker at your local MIND chapter will be able to help. some MIND chapters receive special additional funding to support people affected by self harm.
Hoping that you can find the support that you need and maybe later some talking therapy if you are open to that.
I had a very, very dear friend who has this kind of challenge, so I am not shocked.
Very best wishes