I went to rehab, not kidding, over a dozen times. One of those times in my youth was for an entire year. Others were for a week here and there or a couple of months etc. It wasn't that rehab didn't help me the first few times, I think it was just that most of the time I was forced, usually by the law or some other decree, so I wasn't in any way ready to let it work for me. When I did eventually get sober, seven years ago now, it was not in a rehab facility, but on the couch of an AA members home. Those times in rehab though, especially the ones where I went voluntarily were a great experience.
I too had what could be described as a 'severe' social phobia. I did not allow physical contact with other human beings for about 3 yrs of my life. Being thrust into a setting with so many people, where I was encouraged to speak and 'share' was certainly overwhelming and frightening. For myself though, living the way I had been, I found out that I had been desperately lonely the whole time and wasn't even aware of it. Those experiences in rehab taught me that I could accept help from people, and that there were people who were actually willing to help me, for whatever reason. It was something I needed to learn, because in getting sober, we need help. I do not believe it can be done alone.
I hated that idea at first too. I was not capable of appropriate social interaction by any stretch of the imagination. Rehab and then my integration into AA was a personal battle every day, but it was necessary and it was my only choice. And because of that I can now interact with all kinds of people, in my life and in my work, successfully and its rewarding.
There are also some really good perks to rehab. You can typically eat as much as you want and you don't have to worry about food. There's clean beds and usually air conditioning. They give you pills so you don't claw your eyes out or vomit all the time from detox. It's a positive environment and it takes people out of their normal environment, the environment in which they used drugs and alcohol in everyday.
Another thing that may set you at ease is that there will be people with far more problems than your own in there. Don't worry though, I never felt unsafe or threatened in any of those places and I am a 100 lb woman. Also, don't worry, it is nothing like jail if you've ever been there.
If you leave aside the fact that your life is probably exploding right now, rehab is actually kind of fun. Bare with me here, but its quite a lot like summer camp. Little activities and such. There's some cheese factor to it also. The bottom line though is that its worth it. It's worth it in more ways than you are able to grasp probably at this moment. Seize the opportunity, it may be the only glimmer of light in what is probably a dark world. Enjoy the levity that it offers.