I don't understand WHY - Acne

Okay so I have terrible cystic acne on only one cheek. Seriously, it's nowhere else on my face, except for this big patch on my right cheek. I distribute all product equally onto my face, I keep hydrated and maintain a clear diet, it's not the side I sleep on, I'm not touching my phone or hands to it, I don't use makeup on it, spot treatments only seem to make it worse, etc. I thought maybe it had to be something else since it's only one little patch while the rest of my face is clear. So I went to the dermatologist, and she said that it was in fact cystic acne. I was given antibiotics and a cream but even that's not helping! so seriously why is it just this cheek that's so bad? Please, does anyone have ANY advice or products to use?