I quit smoking 65 days ago. i feel a constant mild headache and have been coughing up phlegm since taking a flu shot about 10 days ago. no other symptoms. is all this normal after quitting smoking?

Quite possibly.: As your respiratory defenses improve, especially the cilia in the airways, it is common for new ex-smokers to cough more. The headache...not so much. Have you had the headache for most of the 65 days, or is it a recent symptom? If the headache is truly constant—that is, with NO periods of time headache free—this should be evaluated. Kudos on taking a giant step to better health and longer life!