do best friends always make the best relationships?

hey someone please help me, ive been in a relationship for 1 year and 9 months(adam)...but i just got involved with one of my best friends(jamie)-ive known him since 8th grade. i liked jamie right before i started dating adam..but he never showed his feelings and i didnt like the mixed emotions, so i just went with adam.. me and jamie have been the best of friends ever since and adam has always been jealous. anyways, about 2 weeks ago, i kissed jamie.i dont know how it happened but it did, and i liked it. ive kissed him twice since then and now i feel like i dont even like adam anymore and all i can think about is jamie. ive heard the quote "best friends always make the best relationships"..and i think its true..what should i do?