{REMOVED}It sounds to me like you may just have GAD, or perhaps very, very slight SAD since you say that you don't get nervous around other people and don't mind going out in social situations.
For people who currently have or who have gone through SAD like myself, the Social Anxiety some days is almost crippling. One of my worst fears was just going to school and being around people. I felt that everyone was constantly looking at or judging me, and if I was ever the center of attention somewhere or had to give an oral presentation I felt as though I would almost pass out from the extreme anxiety. It didn't help either that I had really bad acne throughout high school, and was very skinny/underweight. I feel as though if you had SAD, you would most-likely know it.
If you just seem self conscious of yourself sometimes and that's it, it seems more just like a personality trait than SAD. Is there any reason that would cause you to be more self-conscious than the average person, such as having acne or being overweight? Would you say you're overly uncomfortable about a certain aspect of your body or personality?
The thing that I do kind of notice though is that you said the symptoms came out of nowhere, which is also what happened with me. I was fine until about a few years ago, where I suddenly started having major anxiety issues almost instantly. It was like I had been hit by a truck.
The only advice I would give you is to stop browsing the web for mental disorders and things of that nature, because like you said it does cause more anxiety. When I started having my anxiety symptoms, searching the web and finding all sorts of miserable people with horror stories about depression and anxiety really freaked me out, moreso I think than actually having the anxiety. If you just try to keep your mind off it and stop freaking yourself out by looking around the web for all these diseases and disorders, I would assume you'd calm down a bit if it's not SAD. If you do this and continue to think you have SAD symptoms, the only one you can really go to is your doctor. He can analyze your symptoms and let you know better than any person on here could most-likely.
I hope you find a solution to your problem, and best of luck.