Your cham is very small for it's age and I suspect MBD as well.
There are several problems with your husbandry...I'll address the ones I know now from your posts.
You need to look at gut-loading for feeder insects, carrots and lettuce don't even approach being a good gut-load (read gutload clarification thread that has been recently resurected)
It doesn't sound like this animal has never had the proper lighting. This needs to be corrected now.
Basking light outside of enclosure at a distance and wattage that will create a temp at the basking branch of around 85-90 degrees.
A flourescent tube: zoomed 5.0 or as previously suggested 10.0.
Any calcium supplement online is useless to you at this point. Your cham MUST go to the vet for treatment at this point.
Additionally:
I believe a larger enclosure is needed.
What live plants are you using in the enclosure?
NONE, i have plants, but none are life
How does your cham get moisture throughout the day?
every other day i mist the enclosure, and he has a bowl with fresh water.
What are the ambient temps, basking temp and level of humidity?
don't have thermometer, but temp in enclosure is between 75-90
What supplements are you using and how often?
i have two, TeraFauna ReptoCal, and Zoo Meds Reptivite, every other feeding.
How many different feeders are you offering?
crickets, mealworms, hornworms, silkworms, i tried silkworks and hornworms twice, he never touches them.
You've not had a problem so far because that's how long it takes for it to get this bad and you missed the catching early signs of trouble.
Chameleons are sensitive and specific animals, but they're also pretty tough. It takes about a year to kill one.
Get to the Vet!
-Brad