Allergies in rabbits are uncommon, and I can't see how his sneezing could be caused by shedding. Rabbits shed all the time without sneezing.
I'm thinkingit's dusty hay or pellets. You can try sifting his food and see if a lot of dust comes out, and then if there's an improvement to his sneezing. I'd be surprised if it's anything serious because he's had it for two months, and it hasn't gotten worse. But, it could be, or could turn into, an upper respiratory infection if it is dust or pasturella, and he will need a vet at that point.
The second you see a worsening of his condition, or if it doesn't improve with eliminating dust from his hay and food, you should take him to the vet. A UTI can turn into pneumonia very quickly and once that happens, you'll likely lose your bun.