What Causes Severe Acne On Shoulders Along With Scars?

Hello, I am a teenager girl and I have acne on my shoulders which leaves scars. My shoulders are full of scars and I feel embarrassed of it. I also get a pimple on my face now and then which also leaves dark marks/scars behind. I use dove soap and occasionally a face wash with exfoliating properties. What can i do to treat scars and prevent furthur acne ?