Usage of negation 没 with 在 and 着 particle?
The negation for 我吃着饭 should be 我没在吃饭 or 我不在吃饭, not 我没吃饭. You should change 着 to 在 when you turn the sentence to a negative one.
With this clarified, I think your confusion can be removed. Otherwise, let me know.