You said..."He seems to sit on a branch and is slouched over, very lathargic(sp) lookin"...does his cage have a UVB florescent tube light or does he get direct sunlight? (Neither should pass through glass or plastic.) UVB allows him to produce D3 which allows him to use his calcium.
Is the calcium powder you use a phosphorous-free one? Insects have a poor ratio of calcium to phos. so dusting with a phos.-free calcium powder helps to make up for this. I dust with it at almost every feeding.
Do you use a vitamin powder? Does it have a preformed or beta carotene source of vitamin A? Vitamin A from beta carotene won't build up in the system, but preformed sources do. Vitamin A is antagonistic to D3...so its important that they be in balance. I dust with vitamin powder twice a month
Because my chameleons don't get any sunlight, I also dust with a calcium/D3 powder twice a month.
Appropriate basking temperature is important for proper digestion too.
I gutload the crickets with a wide variety of greens (dandelion greens, kale, collards, endive, ROMAINE lettuce, etc.) and veggies (sweet potato, white potato, squash, sweet red pepper, zucchini, etc.) I have little faith in commercial gutloads because its hard to be sure of what is in them so it makes attaining a balance difficult.
Calcium, phos., D3 and vitamin A are the main "players" in bone health...and IMHO its important to keep them in balance.
You said..."Also when i get near his cage he gets all brown and runs to the back of the cage"...that's normal.