How do I find out if my son has allergies or what is causing his congestion? 12 weeks old.?

My son has had congestion since we pretty much brought him home from the hospital. I do the saline drops everyday, several times a day. I use a humidifier, air purifier and the Vicks vapor heating pads, that put the smell into the air and he breathes it in and I have taken him in the bathroom while giving him a bath in his baby bathtub and turned the shower on scolding hot and steamed up the room hoping that would help. He snores really loud when he is sleeping and some nights it keeps me and my husband awake. I don't know how to get rid of it and he hates having his nose suctioned out, so I would love to find something else that might help. Anyone got any ideas?