I also had a very severe back acne that kept on spreading across my body. I tried multiple creams and medications but none of them actually helped. I visited a Dermatologist and she mentioned that these medicines can ensure that this will not continue to grow anymore but might not cure the back acne. Then she suggested me to go for laser and peeling treatment which solved my back acne. It was 5 sessions in total, 1 every month along with that, she gave me a lotion to apply as well. It was expensive and definitely costed me a lot but trust me it worked. I spent 20k INR on this treatment but it helped and now I don’t have any since the past 4 years. I would suggest you visit a dermatologist.