So who told you to overthrow? Who put it into your head that if you don't strike everybody out on three pitches you stink on hot ice? Who told you this---who told you that---who said you'd better stick to playing the outfield---who shot down your confidence to the point that you'd consider giving up the game altogether?
I would strongly advise you to get together with a really good pitching coach---maybe even a professional pitcher---and have him watch you throw a full bullpen session so he can see exactly where you're at, what you're doing right, what needs working on. And if you're not a rip-roarin' fireballer like Sabathia or Verlander---so what? Not everybody can throw 97 or better; there are plenty of very fine pitchers who just barely hit 90 and who are absolutely devastating because they have, in addition to some great stuff, the control and command of all of it. I was one such---when I recognized that I was not one of those fireballers, I went in the other direction; I knew that if you can't overpower the hitters you have to outthink and outfox them. And you can do it.
I had an absolutely incredible pitching coach years ago. His name was Eddie Lopat, and he was one of the Yankees' Big Three rotation of the late 40s to the mid 50s. He didn't have a real fast ball---but he threw everything else, including the kitchen sink, and when one day I asked him about the slider he responded by taking me aside and showing me how to throw a good one. That led to almost four years in which he worked with me and helped me all he could, which was more than considerable---I became a better pitcher.
So DON'T GIVE UP.