Why are my comedones back if I am using Retin-A?

I was prescribed Retin A last August for comedones. They cleared up, but for the past week, the comedones (or what I think are comedones) have returned very intensely. I am still using the Retin-A so I am not sure why I have these bumps. They're in between my eye brows, on my eyelids, under my eyes, beside my nose, down my cheeks and upper lip.