I need advice

I’m a teenage girl who is struggling with depression anxiety and other illnesses I’m 6 months clean from SH (self h@rm) and I feel like relapsing .
This all happened when I messaged my best friend hi and he completely blew up at me and started to say some horrible things to me for no reason then continued saying “i hate you I hate you I wish we weren’t friends I wish I never met you “ I never did anything to lead up to this point given how much I did for him when he was struggling with bad mental health I was there and helped him when he was self h@rming I helped him through it when his mum gave up on him and started to treat him like sh!t I stepped in and took him under my wing and became like a motherly figure (he’s a year younger) this isn’t the first time he’s done this he treats me like sh!t all the time for no reason and now I don’t know what to do and now I am in a place where I feel like relapsing and it’s all getting bad again I miss him and I miss our friendship but I don’t what to do