Actually, depending on the severity of the infection and your baby's constitution, an infection is an infection...it can cause very high fevers. The excess conjestion in the nose could be causing a form of what we as adults get as sinus infections, but babies sinuses are not fully developed...they won't say that it's an infection, merely rhinitis.
I would be upset with the doctors too. You might want to check his diet and see if you've been feeding him something that he is having a reaction to, such as milk. That one can be a nasty culprit...cause delayed reactions and it takes over a week of abstaining from it to tell if that's the problem. But it can effect both the digestive an respiratory systems...it's worth a try. Then try other foods if you think that the milk is ok.
Keep a humidifier in his room. This should keep his nose from becoming too congested. The flu season can last quite a while and cause recurring infections...you might think he is ok, but then he comes down with things again. I've had the same problem here in my house with my children. IT's been a hard year.
Also, check if you have mold somewhere in your house. Babies are much more sensitive to adverse conditions than were are.
I think those are all the ideas I have for now. Let me know if those work for you or if you need some additional ideas.