I constantly clear my throat due to never ending mucous. I have been this way for over 2 years. What can this be?

Probably reflux. Sleep with the lower part of your neck elevated above your abdomen (semi-sitting). Do not eat or drink anything for 3 hours prior to going to bed. Take Prilosec otc before breakfast and Zantac (ranitidine) 150 before dinner. No coffee, tea, soda, tomatoe products. If you are not better within 2 weeks see an ENT doctor.