I spit yellowish stuff when i wake up in the morning. is it blood or what? i do feel congestion at the back of throat. should i be concerned?

Phlegm: What you are experiencing is not uncommon and may be due to air pollution. It is not a cause for concern. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Yellow phlegm: Phlegm in the morning can be from acute or chronic bronchitis (for example, if you smoke), or can sometimes be from a sinus infection with post nasal drip. If it persists, or worsens, or if fever or pain develop, see your doctor. If you smoke, stop!