Could my kitten have more than just allergies?

I think my kitten has allergies but I'm concerned it might be more. I'm hoping to get a hold of a vet tomorrow, cause I think that's the only time they're open. I'm not sure how old he is, but a good estimate would be around 8 to 10 weeks. He started sneezing a lot about 5 days ago, but here recently, his nose seems to be congested, or at least that's what it sounds like. He has a hard time breathing though everything else seems normal. I can hear him breathing hard when he's awake but not when he's asleep. Could it be more than just allergies?