What Causes Frequent And Stronger Pulsation Under Chin?

I am 77 yr. old female, 5 7 , 147 lbs. In general good health. Had mild TIA 2/2010, discovered 3 leaky heart valves, hypertension. Current issue: I have painless pulsating under chin/upper neck for a month. My head kind of bobs when this happens. It is getting stronger, more frequent. Can you address this for me? Thanks. Mary