“My pitches often have a lot of movement.”
lateral movement to both side is the best goal. If you learn 3 speeds you then have 6 pitches to choose from.
“ My two-seam is known to start off looking like it will hit the batter”, and then it veers back into the strike zone. “
This sounds involuntary because you have not learned why the ball moves laterally? You should be able to get the same movement with a 4 seam!
“ My command is so bad because I have no way to control my pitches when they move in unpredictable ways”
By now you have heard of Rapsodo and others but may not have taken the time to understand what it tells you? It tells you how to design pitch types by their “ball axis presentation”at release. You do not need these great tools to learn this! You just need to learn the concepts and the motor moves to perform them.
“especially my breaking balls and offspeed”
Stay with it, the guy’s that have genetically advanced Velo never learn this and then fail when they need the other. all while your fastball will always be as fast as your fitness and efficiency.
“Is there any way I can maintain movement and also improve control?”
Learn and practice maximally all your pitch types. The change in Velo comes from the lateral movement and orientation of your hand and forearm with each different pitch type.
Learn Ulnar flexion set of the wrist to move the ball towards the glove arm side of home plate. This is performed by having your ball side thumb drive down from forearm pronation to the inside of the ball.
Learn Radial flexion set of the wrist to move the ball towards the glove arm side of home plate. This is performed by having your ball side thumb drive down from forearm pronation to the outside of the ball
“My pitches can fool a lot of batters, but without control, I’ll never be effective.”
Always remember you will improve every time you go out!