My face recently began stinging from workout sweat or hot shower. my face then gets oily (in response) and breaks out in acne. what caused this change? my behavior is the same but sting is new.

Stinging face: You may have developed cholernergic urticaria which is a form of hives brought on by overheating. The acne you describe may in fact be hives. See your dermatologist for a diagnosis.

Here's an idea: I'll bet you have cholinergic urticaria. How this might be causing your acne to pop up in your thirties isn't something that i or maybe anyone else can explain. You're doing well to use topical benzoyl peroxide; you may or may not get extra benefit from using a somewhat pricey preparation. If you're not acne-free in two weeks, or the breakout is still bad, a dermatology consult might be in order.