I have to clear my throat quite often throughout the day because i have thick mucus in the back of my throat that looks like snot when i spit it out.i have no other symptoms.it is worse in am.how do i know if it's coming from lungs or nasal?

Allergies.: That sounds like allergies. Nasal congestion, runny nose, cough, post-nasal drop, headache, facial pains and earache can be triggered by fragrances, dust mites (sweeping the floor), grass, trees, pets, environmental molds and such. There are outdoor and indoor allergens. See a doctor soon, here or locally, as there are medications that may help.