It sucks. I hated having bacne because I was always insecure about wearing tank tops or going swimming. Especially at my track meets because the uniform was a tanktop and shorts. I'd find myself wondering, "when will this end?". And it did. First of all there are only three things I needed for it to stop.
1.) Sun. I layed out in my backyard and got a pretty good sunburn on my back, which dried out my skin making any oils causing me to breakout on my shoulders go away. But you can't just suffer from a sunburn, make sure to treat it with aloe vera.
2.) Neutragena is BAE. The Neutragena body washes all work so well! When you wash your body with them though, make sure to
scrub your back with a loofa (preferably). And more effectively there is a back spray by Neutragena that you can buy at Walmart and it is basically a toner but for your back and shoulders! Can you say, "ah-maz-ing"?
3.) Doing it right. It's best to make sure you get every bit of conditioner out of your hair when you shower because it will breakout and irritate the skin on your back. Also keep your pillows/cases clean. And it's best to sleep with a sports bra or tanktop on at night because the heat from tshirts can suffocate your pores and cause breakouts. And if your a guy just sleep without a shirt.
I hope this helped!