I know how you feel. All my tests for PCOS showed up negative, too - until I gained nearly 100 pounds in a year. No drastic food/eating changes, just a full-body rebellion. My testosterone was off the (women's) charts. I had kamikaze periods. Tired because my blood sugar was high (insulin resistance). The only things I DON'T have is ovarian cysts and sleep apnea, and thinning hair. I am sorry this stuff is happening to you
You should see an endocrinologist who specializes in women - mine actually handles old ladies and their hormone replacement therapy (I'm 26). Even though PCOS is one of the most common disorders among women, most "regular doctors" don't know or understand this disorder. You'll need all kinds of pokey, pee-ey tests for hormone levels, but nothing beats knowing what you've got!
A couple of helpful forums for you are Soul Cysters and Cysterworld. Great ladies!
PCOS only gets worse if left untreated, and losing weight is nearly impossible without treatment. Some people have insulin resistance (pre-cursor to diabetes). I just tell people I'm carbohydrate-intolerant.
I can get more technical about what's happening, so if I can help you, let me know!