Sore throat for 2 months. visited doctors and ent. no bacteria found or mucus. but i keep clearing yellow mucus up. negative for strep/mono. ?

Possible acid reflux: Besides an acute throat infection, sore throats are often caused by acid reflux and post nasal drip from sinus drainage, and potentially from chronic mouth breathing. I would recommend saline nasal spray to thin secretions and a trial of meds to block stomach acid, such as ranitidine or omeprazole. If not helpful, return to ENT for follow up.