Baby has bumps all over body

My son has had the same bumps all over his body since he was 4 weeks old. They started out looking like baby acne and we're only on his stomach and arms. Now he is 10 weeks old and they are everywhere on him but they don't look like acne anymore, in most places they are the color of his skin and feel scaly like he has chill bumps. Some spots still get the red bumps but they just turn into the other ones. Any ideas on what it could be?

We have been to the doctor but he didn't think anything of it