[brutus maximus]

i bought brutus from a kennel/ vet and i have had him for two weeks now and he has a runny nose, sneezing alot and sometimes a lot of snot will come out its not a weird color or anything and at night or sometimes when he is laying down he has a dry hacking cough i have taken him to the vet several times and they gave me clavimox which did not help, benedryl which did not help and temeral which did not help. he is still really playful and eats and drinks plenty what should i do?