One of my bottom teeth has been hurting almost constantly for 3 days. When I touch the spot near the gum line it is very sensitive.?

See DDS. See your dentist for a clinical and radiographic examination to ascertain your concerns,whether decay periodontal problems or recession.
Seek treatment. So many different problems could be causing your symptoms, and even if it's guessed correctly over the internet, you still need to see a local dentist for care. Make the call.