Why do I have small spots on my back and arms?

3 years ago I went to the dermatologist despite not having severe acne but only pimples: I made a treatment with the liposkin foam for acneic skin, the epiduogel gel and a supplement that contains selenium, zinc and vitamin E (only for 3 months the supplement) also for the face always epiduogel foam and a scene cream for blackheads. The situation has now definitely improved, especially in the face. There are still some pimples but for a long time I have small white spots on my arms, shoulders and back and as far as this problem is concerned, it has not yet been solved. The doctor said maybe they came out following the pimples and she didn’t know exactly. These spots are many, I do not have normal and clean skin as everyone can see that in those parts the skin is still acnejca. I think there are also black spots and I don’t know if those white spots are greasy spots, I don’t think they are under the skin and they don’t go away I always scrub. I don’t know how to solve this problem I also want to have clean skin please can you help me with some advice? Thanks in advance