How do you know if you need to bump down the concentration?

Hi, So under my dermatologist's prescription, I began using retin-a .1% every other night starting about 5 weeks ago. I would classify my acne as mild but over the past 2-3 weeks, I believe I have purged and my face has become worse than ever before. Unlike the majority of my acne before, the purge has caused almost entirely large inflamed pimples which haven't gone away or reduced in size in weeks. My face is well-moisturized and I don't really peel anymore, so I was wondering if I'm just going through the purge cycle or if my concentration is too high? Thanks!