What Causes Frequent Head Aches?

Hi, I am 36, 5ft 11, 10.5 stone. I am in good health. I eat healthily & do weekly swimming & yoga. I have 2 children. I am increasingly getting pinpoint headaches - always in the same place in the top left of my head - it feels like it is on the surface, not deep inside. I used to get these headaches when I was singing - which involved quite a lot of pressure to sing the notes. Now, I have given up singing but still suffering from the headaches, almost always in the evening, and with a frequency approaching daily. The pinpoint headache does not often cause me to take painkillers - it isn t that painful it is just annoying and to be honest worrying. Once it starts it will last all evening until I go to bed but will not stop me sleeping. I have once been to the Doctor with these headaches and I was told it was not anything to be concerned about. But I am still worried. I have been getting these headaches for about 7 years, but now with increasing frequency. I would of course like to know what could be the cause. Should I go back to my Doctor. Thanks for your help.