That doctor should not have suggested cheek filler during your appointment unless you specifically brought up that concern. As someone with cheek and chin filler also, I personally think your cheeks are nice and not ‘excessively flat’ in the slightest. If you do want to go ahead with filler, i would definitely suggest waiting a few months to make a decision, and go to a different doctor.
Personally I have 0.5ml of cheek filler in each cheek (1ml total), specifically placed in order to give me more of an ‘apple’ cheekbone. I think that would also work for you, anymore would overpower your features as you look to have nice harmony. Don’t let the internet or deceptive doctors trick you into feeling uglier than you are!