Madisgram, I'm the exact same way (and I'm also bipolar). I can stay indoors for months, my longest isolation was six months. I also lock myself in my bedroom 24/7. Talking on the phone scares me a lot, I need 10-15 minutes of prepping myself before I can make a phonecall.
I need to go to the dentist, but when I was going to the dentist last time - I ended up having an anxiety attack when I was about to leave the house.
It's really a pain. When I'm outside, it's not bad at all, it's just the thought of going outside that scares me; and I enjoy my own company a lot - I enjoy the solitude. I told my psychiatrist about this ages ago and she just said "That sounds really weird". Ugh.
Everybody keeps pushing me to go outside, meet new people etc. I've lost all of my friends because I've been so isolated the past 2 years.
My bedroom is my sanctuary, I can be me when I'm here, I can do the things I want to do and I don't have to put up an act.

There's a song by Joy Division called "Isolation":

"In fear every day, every evening
He calls her aloud from above
Carefully watched for a reason
Painstaking devotion and love

Surrendered to self preservation
From others who care for themselves
A blindness that touches perfection
But hurts just like anything else

Isolation, isolation, isolation

Mother I tried please believe me
I'm doing the best that I can
I'm ashamed of the things I've been put through
I'm ashamed of the person I am

Isolation, isolation, isolation

But if you could just see the beauty
These things I could never describe
These pleasures a wayward distraction
This is my wonderful prize"