Also have you had the teeth checked? Rabbits deal with pain very well but If it is an ear infection should figure out what the cause is. Ear infection is usually a secondary cause.
Yes the ears drip down the sinus. the ears drain to the back of the throat and nose. If the ears are infected the infection is probably making that happen. Be careful I would call the vet she will probably prescribe a different antibiotic. The other one may not have been strong enough or just a...