Low estrogen low progesterone low cortisol reasons??

After feeling terrible for about two years, my doctors finally did some tests and figured out that I have very low estrogen (21 and it should have been between 100-150), low progesterone (1.5 and it should have been 4-8) and low cortisol (don't remember.) Other tests were normal (chol, sugar, t3, t4, total thyroid, etc.) I am a 33 yo female (and my FSH was normal, so not premenopausal.) I am not anorexic nor an athlete. I was a personal trainer for two years and exercised a lot but I have not been for the last year, and have subsequently gained 30 pounds. My symptoms are severe fatigue, depression (on anti-depressant now), some joint acheyness, a lot of sleep disturbance (sweaty when I awake in night,) and cold extremities (have always had the last one.) I just want to know WHY this might be happening. GP's rx is for bioidentical hormones (E3, E2) and prog. THOUGHTS??