I've been sick with a cold, sore throat, coughing, gagging, i went to an instant care in salt lake, yet the doctor said that i'd be feeling better within 2, or 3 days, yet i've now been sick for 6 days now why is that huh? just wondering!

Course varies: The doctor was giving you a rough estimate. The time course for a cold (which is what your symptoms sound like) varies a lot from person to person and virus to virus. It's not unusual to have cold symptoms for 2-3 weeks. Generally there should be no worsening after the first 5-7 days. If high fever, severe pain, or breathing trouble develop at this point, another exam is needed.