Congested Baby

My 3 month old has had a cold for about a week and a half. I took him in, he has no ear infection and clear lungs. We're doing a cool mist humidifier and trying to suck out any mucous. The past couple of says every time I try to clear his nose nothing comes out yet he sounds like there is a lot in there and his nose isn't running. I've used saline to try to break it up but still nothing. Any other ideas on how to help get it out? Maybe once a day he spits up and it's mucous filled so I'm wondering if it's just going down his throat instead.