Why am i sneezing every morning and snot comes out alot?

for the past 3 weeks every morning i sneeze and alot of snot comes out. this has never happend but it every morning and it so annoying. my room is very clean as it cleaned properly everyday and my sheets are cleaned alot too. i dont see what i would be allergic to in my room as nothing has changed. i want to know what is making me sneeze so much and have so umuch mucus ahh. would anyone know. also my diet hasnt changed nothing like that so god knows what it is.