I have had a cold for 14 days, still blowing my nose. Today my head is stuffy and my ears are popping. What over-the-counter medicine can I take?

Not unusual. Unfortunately for some, a cold symptom may last 2-3 wks. If you are not having fever, no sinus/facial pain/headache (signs of sinus ifections etc), you probably be ok with some otc combo meds (antihistamine+decongestant)/advil-cold-sinus etc...Afrin (oxymetazoline) spray may very quite effective, but no more than 3-5 days of use. If symptoms worsen, consult doc.. Good luck.
OTC cold medicines. Probably the most useful otc product for your symptoms (presuming you have tried the usual decongestants such as claritin, claritin-d, or sudafed) is a 12-hour nasal spray like afrin or neosynephrine. These are very potent nasal decongestants. The only caution is that they are not to be used for more than 3 days, but after that time usual decongestants should work again.