I've definitely been in that situation before. With BDD, I used to isolate myself in my room all day for days because I felt I was too fat and ugly to be seen by other people. I skipped classes, missed work, and passed on hanging out with friends because I was too self conscious about how I looked.
One day, I eventually had to take out the trash to the dump outside my apartment complex. It was the strangest feeling walking outside in the sunlight, but it felt amazing and freeing. It was a super short walk, but it was that super small baby step outside that made me feel like it wasn't that scary being outside. It reminded me of how nice it was to be out of the house, and it made me want to be outside a little more.
Make it a goal to just take that one first step. The journey of a thousand miles begins with just one step after all. Eventually, you can progress to being outside and being around people longer and more comfortably.
Also, it helps to stop thinking so much about what you want to do, and just do it. I had the hardest time getting back into exercising after I fell into my slump of staying indoors for days, so one day I just sucked it up, changed into my running clothes, and forced myself out the door before I could talk myself out of it. I started running, and there was no turning back. The anticipation and fear we build up in our minds is something we can overcome if we just stop overthinking and do more.
Good luck with everything!