Synthroid and welbutrin xl

I was born without a thyroid gland so I can't compare the way I feel now to the way I would've felt with a thyroid. I've been on Synthroid my entire life (22 years), and I'm up to 112 mcg now. I am very skinny (5'5", 104 lbs) and feel constantly fatigued no matter how many hours I sleep, what I eat, and how much exercise I get. I periodically get pain in my hip joints, heart palpitations, and intense mood swings. My thoughts race but I have very little physical energy. I feel restless and gloomy almost all the time for absolutely no good reason. My doctor tells me I'm depressed but I honestly have no reason to be depressed and I wish she would see it as a symptom instead of a diagnosis. I graduated from a good college, I've got a job I like, I have friends, I enjoy life and my hobbies, yet I feel overwhelmingly sad. This does not seem like depression to me.

I find that after I do aerobics I get a tightness in my chest, which makes me worry about my heart, but again my doctor doesn't seem to think this is cause for concern. I have been irritable/fatigued for YEARS and I suspect I'll feel this way for the rest of my life. The worst of it started when I hit 16 years old and started the 112 mcg. My tests are always normal and it frustrates me that my doctor disregards my symptoms. I've tried other doctors, but they always send me away with my 'normal' test results. Can anybody help?