Does this seem like a thyroid problem? I've felt a bit "off" for a few years now, but lately I've been feeling pretty awful.  I'm fatigued almost all the time, and have to nap even if I get plenty of sleep.  Sometimes I get random chest pains or my heart flutters.  I feel like I'm not getting enough oxygen when I breathe, and that I'm mentally dull/slow.  I eat constantly but can never seem to gain any weight.  I overheat very easily and sweat even when it isn't hot out.  I randomly have a bout of diarrhea almost every month, and often have abnormal abdominal pain before exciting events.  I occasionally have manic phases where I can't sleep and my mind races uncontrollably.  Lastly, my muscles (especially my arms) are really weak, but I'm pretty out of shape.

I've done some research on my own, and am planning on seeing a doctor at some point.  I'm just curious if anyone here has experience with thyroid problems, if they had similar symptoms, and how they turned out with treatment.  Any other general info is welcome.

Summarized question: Are fatigue, chest pains or heart flutters, feeling mentally slow, eating without gaining weight, overheating very easily, diarrhea, abdominal pain, manic phases, inability to sleep, racing mind, and weak muscles symptoms of thyroid problems?