Missed Period, Please Help! (on the Verge of Tears)

Alright. Any help/advice at all would be greatly appreciated. The thing is, I haven't had my periods for a little more than four weeks (past approximate due date). I'm still a virgin so I know pregnany is out of the question. And i'm 20, going to be 21 soon. Along with the missed periods, I have the following symtoms and conditions.

1. Hot flashes at night. I'm not even sure if they should be termed as hot flashes but I get incredibly hot and sweaty, especially at night, despite not doing any sort of sweat-inducing activity.

2. Excessive growth of dark hairin the past year around places like chest, stomach, face. Some of the chest hair is so wierd, if ipluck at it with my fingers, it comes right out!

3. I'm extremely obese. My bmi falls at 41 or 42.

4. Acne. Then again, i've always had bad acne since I was 12 so I doubt there's much difference.

I've read about pcos but it's scary to think that i'm only 20 and could be suffering from it. I also read about secondary amenorrhea, which can be caused by extreme obesity, as one of the factors. My question is, could this stopping in my menstruation be a result of pcos? Or am I just being overly paranoid and substancial weight loss can cure this and make me regular again? In other words, has this ever happened to anybody?

I'm pretty much a nervous wreck. Any input would be appreciated immensely. Thanks!