How to get rid of skin marks on chest? (Pic)

So up until about a month ago I struggled with really bad body acne, until my dermatologist put me on a new medication that's working considerably well. I only have 1 actual pimples right now, but it looks like I have way more because of the marks I have from the old acne and it's really irritating, especially because of where it's located and how pale I am (making them super obvious). They're all flat and most of them are brown, and I have a few that are reddish. I always cover them with makeup around my boyfriend (not because he'd care, but it makes me feel better). Does anyone know how I can get rid of these?