Thanks again to both of you guys.

I saw this doctor towards the beginning of March, as my resting HR had doubled overnight (normal is around 40-50, was over 100 when I checked). I monitor my pulse pretty frequently because I was diagnosed with two minor heart problems in high school; patent foramen ovale (a relatively common heart defect) and sinus bradycardia (resting HR < 60 bpm).

I had another EKG and she referred me to a cardiologist. I wore a 24 hour holter monitor and my heart was okay. My resting HR is back around 50, but still no explanation for the tachycardia. My own hypothesis is some sort of electrolyte balance (my potassium was low in a recent blood test). I think I need to be more vigilant with refueling during long exercise and probably more fruits and vegetables wouldn't hurt either.

I might see if I can get another doctor to order a bone density test, but I feel horribly guilty asking for something I don't "need." I am not worried so much about my current health status, but more of what damage may have been done in the past. I think I might ask my PT about exercises to help build up bone density. I did used to run a lot, but with my recent knee injury, I have been cycling more (and I am aware that it can have a negative effect on bone density).