First off, I have to say that you are a real person. Maybe you aren't the person they remember, and maybe you don't fit into some box that society requires, but that doesn't mean you're not a person. You are a person who is struggling with a very real illness, and that doesn't make you less human.

As for reaching out, maybe honesty is the best. Tell them that you have been struggling for a long time. Tell them exactly what you just said, that you don't want them to see what you've become. But do tell them you miss them.