Ok for a 5 month old chameleon you want to feed every day unlimited. They can easily take down 2 dozen or more insects a day at this age... When you reduce is largely based on if you have a male or a female. So I need a bit more info on that first before I advice you.
Per supplements. Calcium without D3 is used at every feeding lightly dusted on all insects. Then You want to use a multivitamin that has A and D3 in it 2 times a month say the first and the 15th. If you take pics of your supplements labels I can give you info on if you have the correct ones or need to switch anything.
Can you post a few pics of the chameleon as well so I can see overall body size?