Do you think I have potential to be a decent pitcher?

During your pitching sessions, throw a little more pitches after you feel like you're getting tired so you can raise your endurance. Even if you don't throw as hard, just keep the same arm motion. Eventually, you're going to be able to throw faster because of that extra stamina. It's like running; the more stamina you have, the faster you could run because you have more stamina to use up.