Okay. First, let me begin by saying that you're not a disaster.
Relax.
I was like you - overweight, sick, lethargic and confused. I learned - a lot by trial and error - about what works and doesn't work for my body. What you have to do is to take a modicum of effort and research ways to be healthy. It's not enough for someone to point you in any given direction and say "Go!". You have to begin to understand what your body wants and needs to be healthy.
A lot of your condition - the depression, agoraphobia and like is a direct result of your diet. I was on 6 direct psychotropic drugs for mood stabilizing, enhancement and encouragement - swapped out a few burgers for veggies, dumped the carbonated beverages and the meds went away. I'm certainly not a medical professional - but I can make a clear distinction between what goes into my body has a direct correlation to what happens to my body.
Ok - so you want to get healthy? I would start with what you have - you have here (Reddit) and there are a lot of good solid subgroups that offer dieting advice (/r/keto, /r/paleo, /r/diet). Dieting isn't so much about giving up things - as more as corrective thinking habits. I still eat cake - just not for breakfast every morning.
Stop taking the multivitamins - they will do nothing more for you that you can't already get out of food - and depending on the vitamin - may be causing you more harm than good.
For exercise, start small. Walk around the block - your neighborhood or your district. It doesn't have to be marathon training - and you wont have to talk to anyone (or interact). Or, like me, join a gym that is open 24-hours (Planet Fitness is great fun at 12:00 a.m. - just me and the janitor!).
Whatever you do - don't give up. You need to begin this venture with a clear purpose to see it through to the end. Not everyday will be sunshine rainbow being blown up your ass - but, you will eventually get there. Diet and exercise have great power over your psyche and your social life.
If your ready to begin, make a plan. Find a sensible eating plan to get you started and go. Enjoy, be safe and come back often for encouragement.