When you open an egg as you describe, with the milky or creamy appearance inside, it is bad, and no significant embryonic development ever occurred. After 5 months, any good egg (or egg that had significant development) will first dribble out clear fluid when you cut into it, unlike the milky appearance you described. The current outer shell appearance indicates nothing at this point. If curiosity is killing the cat, using small fine-point scissors, like cuticle scissors, you could cut eggs until you find a good one. Not only will you first encounter the clear liquid, but you then should have no trouble finding a developing chameleon. If and when you find one, then stop and be patient on the rest. I would be more encouraged if you had found clear fluid and some embryonic development, even if the embryo had died during development. That is still reason for optimism with the rest of the clutch. To find the milky appearance you describe normally bodes poorly for the rest of the eggs.
The Chameleon Company