When I went to Biola in 1971, I had no idea that one day I would become a Greek teacher. But ever since I was 16, I had had a crazy passion for God's word and knew enough to major in Biblical Studies. Later I started on my M.Div. and was invited to teach Greek at Biola. The focus began narrowing, until today I can look back and say (with gratitude and some relief) that I found God's calling for my life. Even though my years in high school were fuzzy, looking back now I can see God's hand was preparing me for my life's work.
Friend, just keep moving forward in your walk with the Lord. Let him sort out the "when" and the "where" of your life calling.