I agree with Morte---do please see your provider and be checked for allergies. I've heard that mold can develop in the ventilation systems in health care facilities---even the cleanest facilities---and sure enough, my chronic sinusitis flares when I'm working in a hospital or LTC. My symptoms would be very similar to those of a cold: stuffy nose, headache, sore throat---but the cause was the sinusitis, not an actual cold.
You could also try a Neti pot to decrease your stuffiness. I haven't tried one myself---as much as I believe in holistic remedies, this just seemed a little too gross for me.
I also agree with previous posters that you're being exposed to a lot of new bugs working in the healthcare environment. Again, make sure you wash your hands carefully. The alcohol-based cleansers are good for getting rid of most upper respiratory bugs but they aren't effective against c.difficile, which causes particularly nasty diarrhea. Make sure you wear your gloves when toileting residents with suspected c. diff (well, wear them when you toilet ANYONE!) and wash your hands with soap afterwards.
Don't be shy about wiping down computer touch screens, keyboards or telephones when your co-workers are sniffling and sneezing. Not only can you get sick from your residents and their visitors, you can also catch whatever you co-workers might have as well. Frankly, I think it's ridiculous that any health care worker who has a cold is expected to come in and work because they expose the residents or patients and their co-workers to whatever crud they have but health care institutions take a pretty grim view of anyone who calls in "too often."