Welcome to the forums and thanks for reaching out and being here. I'm sorry that you're going through this.
So there's this great book I'd recommend... (just kidding) :P
I do not understand what you're going through, because I haven't been in your shoes - but I do understand losing your independence, losing your friends and not knowing why you are unwell. It really is a downward spiral sometimes - especially if your Doctors/Specialists don't seem to have a lot of hope or direction in where to go. Your story is very relatable to my own.
So - to your question -
Who can be your support group now? I did lose a lot of friends in this, but I also gained a lot of friends. For me I used a lot of social networking, but ultimately which ever way you choose - you may be alone in your bedroom but you don't need to feel alone. There are a lot of people going through similar things as you.
What do you enjoy and where can you grow? Yes - this is where the books come in (sorry!) but we need something to help us feel sane! Are there other things that you enjoy? Or maybe volunteering or courses? There's so many you can do online or self-paced. Quercus mentioned brainstorming and this is so important - finding out where your capabilities are now and how to work around them.
Find things that help you feel good. Thinking about people having the best time when you're not is the sure fire way to have the worst time! What can inspire you? What can get you going?
Personally - I really got a lot of benefit out of www.chronicbabe.com (the YouTube videos and the articles) because I needed to see people who were dealing with their own chronic illness and still having a good time. Maybe you'll like this one too.
I hope this is a good place to start! Feel free to jump in or ask any questions if you like.