Skin: acne-prone esp forehead, dehydrated, sometimes oily & sometimes dry and flaky, lots of sensitivities (eczema or acne) to laundry detergents, lotions, shampoos, conditioners

Current products: CeraVe foaming cleanser & CeraVe PM (been using for 1 week, morning & evening)

I previously (for maybe 10 years!!) used an acne controlling routine centered around benzoyl peroxide and physical exfoliation. I have since seen the light and am starting afresh to try to heal my skin.

Question: I've taken a very slow and cautious approach to introducing new products - I want to use a product for 1 month before 'approving' it. Since starting the CeraVe, my skin seems to like it - several pimples have disappeared and no major breakouts. But I've started noticing a few painful-ish bumps on my forehead near my hairline... Is this a reaction to the cleanser / lotion? Or is this just a 'withdrawal' from all the benzoyl peroxide I used to use - like my acne had been controlled by the BP, but now I don't have any actives in my routine, so now it's free to come back? Basically how do I tell the difference...