I've ordered from petdrugs.com for my hedgehog before

because he had ear mites. I plan on placing another order for flea medication for my yorkie this time around but I'm lazy and haven't gotten around to it. They have a lot of medications that you would normally need a prescription for in the united states as OTC over there since its a company based in Canada. I guess people in canada believe that medications for pets should be more accessible to the people so that they can actually provide care for the pets and not have vets trying to make an extra buck or two. Their prices where the cheapest that I found it to be online, shipping was kind of long but the product arrives eventually and everyone is happy

. I'm a student so I know what it means to live on a budget. I would also suggest looking for clinics that offer wellness visits. The one that I go to is $20 for each office visit + anything else that has to be done for her although they can't provide services for everything and you will still need to find a vet that is a full service clinic.
As the other people suggested, I would find a new vet. Science diet is horrible food and you don't need anyone to tell you that. Just take a look at the label and you know its junk. I have my puppy on buffalo blue and it is terrific food. Good luck!