Well, the good news is that these conditions are not necessarily permanent. I experience two such periods in my life, and if I had not had this issue I would have dismissed anyone making such a claim as a nut. A depressed immune system may be one cause. So can a traumatic experience (in my case). I would suggest ordinary valium, which unfortunately has become as controlled substance. Valium is a really safe wonderful drug albeit it can be addictive. Decades ago, when I worked an an ER you didn't even need a prescription to get it from the pharmacy. Now the drug bureacracy has declared it "dangerous".
Zoloft can take something like eight weeks to fully kick in. Until then try meditation I know it might sound silly but teaching yourself to relax can really make a bug difference and that's important because there is unfortunately no magic pill. Also make yourself get out even when you are at your worst try to be strong and push through! These are not weird mental problems they are actually quite common, talking about it helps also meeting people with the same issues, talking to a therapist who can teach you how to handle and work through it. When you feel like someone is looking at you remind yourself that person might like your shirt or wonder if you are someone they have seen before and people are so busy in there own life chances are most of the time its just in your head and these are people you will probably never see again. Good luck!