I am on my second course of Doxy 100mg per day and after the 4mo period, i am starting to break out again. I have moderate acne only above teh cheek. I was taking brand called Duradox... but today, I was given Vibramycin which is Doxy also but the derma claims it is a better doxyxycline??? My guess was I became resistant to doxy since i am breaking out after 4 mo of being clear just to be prescrived doxy again? what do u guys think?