My persian has black earwax and she shakes her head occasionally (just started a week ago) last vet visit she?

week ago, last time vet said it was wax not mites cleaned it up,it seems like it really bothers her. it is black grasy and waxy,,shes an inside cat but loves the porch. Should I bring her in to the vet to be sure? my first cat,always had dogs before. I just wish I knew the difference as vets are expensive.