For the last few days, i have 2 out of 3 pain at right side of head / headache. it feels like throbbing pain as per intervals. what could that be?

There are several: types of headaches, sinus headaches being one of them, muscular tension, and vascular are others. You won't know what you have going on until you see your doc. He/she can rule things out and identify what is happening and treat if needed. Consider biofeedback or clinical hypnosis (www.asch.net) if they continue. Peace and good health.