Could it be a reaction to the retin-a and not dry skin? I'm wondering that because if nothing is touching it, I would think it's not run of the mill dryness.
I have an oily t zone, but dry cheeks. When my cheeks get super dry, I apply my retin a, wait 20 minutes, apply a thin layer of emu oil, wait about 5 minutes, and then gob on the cetaphil moisturizer. This helps a lot. Also, if you have some dry flakes and don't use a clarisonic, try using a buf puf (gentle one since you are on retin a). If you still have flakes, try an enzyme exfoliator, such as Mary kohr lily essences enzyme exfoliator. It's super gentle because it's not abrasive, but gently dissolves the dry flakes.
I love First Aid Beauty's Ultra Repair Cream. I use that in combination wtih Yu-Be Moisturizing Cream, and it was a lifesaver this past winter. Both can be found at Sephora.
In addition to moisturizer (not at same time) I use Josie Maran Argan oil once or twice a week, it pretty much gets rid of all dry and I live at a really high altitude (8000 ft) so the climate here is insanely dry.
I also use Cetaphil on my derms rec and at night I use Origins because I like the smell and it doesn't irritate my skin and my skin looks great from it.