If you're having trouble with the curve (now there's a movie title for you!), you might do well with the slider---this has been the case with a lot of pitchers. Actually, the slider is a pitch that is not as fast as a fastball nor as sharp-breaking as a curve but which is easier to throw and control than either of the other two, and if you throw it correctly you can get a sharp late break on that pitch...The grip for the slider is offcenter, with the index and middle fingers very close together and the middle finger just touching one seam, fourth and fifth fingers curled up on one side of the ball and the thumb underneath, sort of cutting the ball in half. My pitching coach told me, when he was showing me how to throw the slider, "Throw it like a curve, but roll your wrist, don't snap it." just turn it over. I threw my curve with a sharp karate-chop wrist snap, so to throw the slider I just had to ease up on it. I got the hang of it in about ten minutes, but I realized that one does not master that pitch overnight, so I spent some months working on and refining it. The slider became my strikeout pitch and served me very well in that capacity for more than two decades.
You might also try a knuckle-curve (my second-best pitch). It's simple enough: you use any one of several knuckleball grips and throw your curve; it comes in there looking for all the world like a fastball and then suddenly drops, much like a glass hitting the floor and shattering into little tiny bits and slivers! That too can be a devastating pitch. (I built my entire arsenal around those two pitches.)
And my pitching coach also told me that just about anything I threw could be turned into a nice changeup, and he demonstrated several for me and showed me how to throw them. You might experiment with a couple of them; you might be surprised! Remember one thing---whatever you throw, you have to throw everything with the same arm motion and the same arm speed as your fastball. You do NOT want to telegraph any of this; it's a definite no-no! :baseballpitcher: