Congratulations on the bike!!!
I would ride with you if only i could!
You said you just upped your vitamin D... that will aid your calcium uptake naturally, you know? From food. It might be good to have your calcium level or even all electrolyte/mineral levels checked with your next blood draw after 3 months though, as that is how long it takes for the new vitamin D level to stabilize.
In any event, if you do take extra calcium, make sure the ratio of Mg:Ca supplementation is not greater than 1:2 in favor of the calcium.
That is great news that you are getting a some more sleep. the Celexa could be contributing also. You might actually try removing the melatonin at this point... generally that is for adjusting one's sleep cycle i.e. it should do it's job in a short period of time (few days or a week). Plus, you could always start it up again if necessary.
I am really wowed about the bike. You take it easy though, and start out doing just a bit at a time... just a few minutes at first... you will build up if you do it regularly. regularity is more useful than overdoing it (which can actually be dangerous).
Have fun with it!
Gosh i am so happy for you!
~ waves ~