What medicine can treat acne scars on my upper back?

Hello doctor,

I am a 31-year-old male. For no reason, my upper back has formed acne in the back of my shoulders and in the mid-upper back. I tried Benzoyl wash, Vanoxide Topical, and Doxycycline. There was no success. I am now using Hibiclens foam wash, Clindamycin and Benzoyl foam, and a Sulfamethoxazole tablet two times per day. This second regimen has only been going on for five days. How long can I expect results?

I also shave my shoulders which I know puts me at risk for folliculitis and other related conditions. However, I have never shaved my back and therefore do not understand how this occurred. Just when I think things look better, a trip to the gym and shower right afterward, it always makes things look worse. Am I wasting my time trying to fix this? Of note, I had very severe acne on the upper back and face when I was a teenager. I was on Doxycycline in the past.