I agree with Bosox that velocity---or speed, whatever you want to call it---is overrated. There are plenty of pitchers around who, no matter what they do, will never be able to throw 100 miles an hour or what have you.
So---you could become a finesse pitcher, develop a good arsenal of breaking stuff, three or four such pitches, and work like mad on control, placement, keeping the batters off balance. And you'll find that even an 81-mile-an-hour fast ball will look as if it were coming in there at 100 miles an hour.
I remember my pitching coach telling me once that he threw a so-called fast ball at 85, 86, and to the batter it looked as if it were coming in there at 106, because of how he set up his pitches. I myself managed to find an 81-mile-an-hour fast ball, and he told me that I could use that, along with my other stuff, to set batters up for old Filthy McNasty---the devastating slider that was my strikeout pitch. So don't worry about the speed. Concentrate on control, on working to the corners, on getting the ball smack-dab into the pocket of the catcher's mitt, and you'll come out all right.