Hello,
It looks like candidiasis and oral thrush to me. The red dots on the buttock can be small irritated hair follicles. Thrush appears as white patches in the mouth. Usually they can be seen on the tongue, inside the cheeks, under the tongue, and in the back of the throat. I suggest you to get an examination done from your doctor and get a KOH examination of the scrapings done of these white coatings.
Nystatin (Mycostatin) liquid is used by swishing a bit in your mouth several times a day and then swallowing the medicine. Throat lozenges called Mycelex trouches can also be used. If the symptoms are severe then oral antifungals may be needed.
I hope it helps. Take care and regards.
I sometimes also get pimple like dots on my butt :(