Sounds to me like an ear infection/ yeast in the ear. I would assume its ears are down, therefore they tend to get ear infections a bit easier since the ear never can dry out.
So here is what you do
I use Vet ear wash, but warm it up some in the microwave and put it in a plastic syrenge. This way it feels nice since it is warm.
They will shake their head, that is what you want them to do, next apply the medication,. This will stop the ear infection, you will need to do this for atleast 7 days. Then keep an eye on it. Easy way to tell if it is an ear infection is their ear will smell nasty,,,,,kinda yeasty/ dog smell
My dog is really prone to this, so I do the Vet wash once per week. Havent had a problem since
I doubt it is ear mites since you get a waxy gunk from his ear