Has your primary care doctor referred you for a psychiatric consult? For years doctors kept saying, depression, depression depression. NONE of the usual anti-depressants (mainly SSRIs) would "poop-out" or would make me worse/manic. Recently I went so low and my symptoms were just like yours. I went in for a psych consult, they diagnosed me as Bipolar II-- different than the usual form of Bipolar in that you have mood swings, but no mania, and that the mood swings tend to go down further than usual depression. ONe of the things the psychiatrist really asked me about was changes in eating habits especially eating more carbs or sugar. They have put me on a mood stabalizer instead of a usual anti-depressant. It couldn't hurt to try to see a psychiatrist sooner than later as you have to wean onto most psychiatric drugs. I have been weaning onto Lamictal for a month now, and am still not at a doseage level that is considered to be effective.

Good Luck!