No, you don't have to become a preacher in order to serve God! God uses all kinds of people in all kinds of situations -- men and women who are dedicated to Christ and are seeking to live for Him.
In fact, some of the most effective witnesses for Christ I've ever known weren't preachers at all. They were stay-at-home moms, factory workers, clerks in stores, lawyers and salesmen, even politicians and presidents of large corporations. In spite of their differences, they had one thing in common: they loved Christ, and they loved others in His name. They often met people no preacher would ever meet.
The most important thing you can do right now is to seek God's will for your future. Make it a matter of prayer; discover the gifts God has given you; seek advice from godly people who know you; let the Bible be your guide. If God has some type of ministry in your future, He'll make that plain. But even if He only leads you one step at a time, take that step and commit it to Him.
Most of all, put Christ first in your life, now, and always. Let nothing divert you or keep you from Him, but make it your goal to live for Him, wherever He leads you. The Bible says, "Finally, be strong in the Lord and in his mighty power" (Ephesians 6:10).