So I found this site a few months back and have looked through the forum topics dealing with acne in general. I have been using the Tretinoin cream for a year, and towards my last year of high school it suddenly stopped working and I began to break out again. After I went to the dermatologist over the summer, it was also informed to me that this medication was no longer covered. I did not want to pay hundreds of dollars for it. So i resorted to using a drugstore 5% benzoyl peroxide for a while. The summer following that I broke out really bad all around my mouth and on my eyebrows. I started university and had to go to school for the first time without confidence.
I took towards getting the regimen as my last resort because of all the positive reviews that I have read about. I have moderate acne, and the first few days of using the regimen I cleared up dramatically. As the week went by probably on my 4th and 5th days I began to break out really normally again, about 3 pimples a day. I'm not sure why this happened, but I hope that I would get through it.
The first few months may feel like a roller coaster ride with ups and downs, breakouts and clearing, but as time goes on the breakouts should become smaller and heal quicker before. Usually by the third month most people are clearing up nicely.
To answer your question though it is very typical to see a breakout as you are approaching week 2.