By Brandy McDonnellA version of this story appears in Friday's Weekend Life section of The Oklahoman.'Underdog' success story: Texas country hitmaker Aaron Watson to play Oklahoma State Fair's Xtreme Bulls concertsMore than 18 years and 2,500 shows into his country music career, Aaron Watson has a little trouble remembering if and when he’s played specific places.Whether he’s been there before or not, though, the Abilene, Texas, denizen said he is looking forward to performing at this year’s Oklahoma State Fair.“I think they told me that the last three years we’ve played like 40-something states and 11 countries,” Watson said last week, just after returning home from a nine-day tour of Europe and the U.K.