Congested cat? HELP?

I took my cat to the vet ahwile back because he had a cold, they gave me antibiotics. Ive been giving them to my cat and he isnt sneezing anymore but it been 2 months now and he is still congested.He is fine he dosent have any symptons like he did before. He isnt gonna get any better if he dosent get his snot out. He dosent know how to blow his nose lol. I tried using that blue thing to suck it out but it really dosent work, and the vet said nothing they could do. I tried putting him in the bathroom with the shower on so steam could brake it up, didnt work...help?!!??!