I went through such similar emotions when my AH went to rehab. He'd caused absolute devastation and went off to months of world class care while I struggled to come to terms with the bombsite that was my life. It did not seem in the least bit fair.
I then got a call from his rehab people inviting me onto a free retreat for families of addicts. He said they did recognise we got left behind.
Does your A's rehab do anything similar? Are there any charities you could contact for support for you?
Wishing you peaceful times ahead.