First of you should not feed your chameleon mealworms. 2-4 appropriately sized feeders a day, and sometimes every other day, make for a healthy chameleon. Your chameleon should never know when he is going to get food, so switch up when and how often you feed him.
You may want to prick your phoenix worms with a pin so that they can be digested, if you do not they can come out perfectly in-tact and alive the next time your chameleon defecates. Try other feeders like roaches, snails (cb), silkworms, hornworms, moths, etc.