It's probably just a cold. It's super important, expecially you have kids to do a lot of hand washing in your household both you and guests. And I know it's tough, but ask people to watch the kissing...
Colds affect little babies wore than older ones because their nasel passages are so small. That's why new babies sneeze al lot. The only thing you really need to watch is that cough. Coughs can turn very dangerous in babies very quickly - strider, croup - do a little research on these, and listen closely.
If he feels badly, that's why he is sleeping more, and if he is congested,it is probably hard to suck and thus he needs to eat for a shorter amount of time but mroe frequently.
IF his appetite decreases, you need ot ocunt wet diapers and call the doctor. That could be the flu.
Medication (other than Tylenol for feversI is not approved any more for that age. Use the cool mist humidifier - it really does help both for comfort and white noise. Try not to worry too much, jut be attentive to changes in his behavior. Enjoy youn new son!!