I havn't had a heachache in 6yrs, how come i don't get them anymore?

when i was 14 i use to get unavailable sever headaches almost every day!!!!, they got soo bad that i missed a lot of school!!!!, anyway, dunning the summer of 2005 i got a wicked sever headache, it was soo horrible that i cried for hours on end!!!!, on the way to the doctors (driving in the car with my dad), i felt a huge POP in my head and then all of a sudden my my headache went away and i haven't had one since!!!! not one!!!!!!, i use to get sever headaches from the ages of 6-14... im 20 now .