Beagle puking.... any suggestions?

So for the past month, my 4 year old beagle has gotten into 3 puking sessions. When he starts to gag, we try to rub his belly and throat, which helps, but he will take an hour to two to get to the point of actually vomiting. When he finally does its his dinner and all the hair he licked up from the carpets. We haven't changed his food, he has been on the same brand for about 2 years. Our heeler has had no issues with puking.
Any ideas? We have an apt with his vet, but not for a few days, thought we could get some ideas on what it could be.
Thanks