I'm sorry that Mascot has been sick
There are many people, like you, who didn't know about pet stores selling puppy mill puppies until coming to YT. I'm sure there are plenty of people who have purchased from a pet store and have been lucky enough that their dog is healthy and some that have not been so lucky. You are doing all you can by giving him the medicine and taking him to the vet.
Don't be too hard on yourself! Just love little Mascot and take good care of him
