I have been getting headaches with mild pulsation on the right side of my head. why is that so?

See a doctor: You may be suffering from a type of tension headache or a more serious condition called temporal arteritis. You need to see a doctor asap for more workup including labs. If it is termporal arteritis, seriousl complications can occur so you don't want to put it off.

Headaches: Your headaches could be coming from tension, eye strain, tooth grinding, dehydration, lack of sleep/poor sleep, skipping meals, stress, sleep apnea/snoring, or chronic sinus problems.