I have been congested for 10 days -- much longer than a regular cold. antihistamines help a little. what else can i try?

Still a cold: A viral upper respiratory infection may last up to 2 weeks, although usually it lasts less. Beyond 2 weeks symptoms may suggest allergy or complicating sinus infection. Antihistamines don't work well for colds. You may try nasal irrigation with saline, even a nasal decongestant such as oxymetazoline (afrin) for no more than five days. If no better then, see a physician.