Sidney Wilson’s St. John’s career is over before it started. A little over three months after committing to his hometown school and the day before fall classes begin, the four-star wing from The Bronx is leaving Queens. In stunning, somewhat unprecedented news, the 6-foot-7 Wilson will transfer, a source told The Post on Tuesday. Wilson has been unhappy since arriving at St. John’s for the summer session and has flip-flopped on whether to stay or leave, sources said. Initially, he planned to stick it out after meeting the coaching staff Monday, but Tuesday, he changed his mind, sources said. Wilson had missed several team activities in the spring such as weight-lifting sessions and workouts. After meeting with coach Chris Mullin and deciding to try to make it work, he shaped up, but still remained unhappy. Wilson lost his mother, Paulette, in March 2015, when she passed away from a heart attack at the age of 50. He left St. Raymond to attend Brewster Academy (N.H.) in fall 2016. Being back home offered too many distractions, according to sources, and he felt it was best he leave the area.