How can I generate a random number without a page refresh/mouseClicked

So I know that because the random number is being generated in setup I'm only getting one value but when I call the random number in draw I'm getting too many numbers. What I need is for when the pitch leaves the screen, a new number is generated and a new pitch is thrown based off of that number.

var pitch; 
var speed;
var xMovement; 
var x = 300;
var y = 200; 
var a = 400;
var b = 200; 
var num;

function preload() {
 data = loadJSON('pitcherData.json');  
}

  function setup() { 
  createCanvas(600, 600);
  num = random(0,100);
} 

function draw() { 
  background(220);
  randomPitch(); 



}

function fastball(){
  var FAMax = data.pitchers[0].pitches[0].MaxVelo;
  var FAMin = data.pitchers[0].pitches[0].MinVelo;
  var FAxMov = data.pitchers[0].pitches[0].xMov;
  //mapping of maximum velocity 
  var FAMapMax = map(FAMax, 50, 101.3, 0, 8);
  //mapping of minimum velocity
  var FAMapMin = map(FAMin, 50, 101.3, 0, 8); 
    // mapped xMov of fastball
  var FAMapMov = map(FAxMov, -9.0, 5.0, -7, 7); 


  // pitch velo will randomly vary between max and min
  var FArandomSpeed = random(FAMapMax, FAMapMin); 

  fill(0,200,100);
  ellipse(x, y, 30, 30);  
  y = y + FArandomSpeed; 
  if(y>400) {
  x = x + FAMapMov;
  } 
  if (y > height*2) {
  x = 300; 
  y = 200; 
  }
}

function slider(){
  var SIMax = data.pitchers[0].pitches[2].MaxVelo;
  var SIMin = data.pitchers[0].pitches[2].MinVelo;
  var SIxMov = data.pitchers[0].pitches[2].xMov;
  console.log("Mov: " + SIxMov);
  var SIMapMax = map(SIMax, 50, 101.3, 0, 8);
  var SIMapMin = map(SIMin, 50, 101.3, 0, 8);
  var SIMapMov = map(SIxMov, -9.0, 5.0, -7, 7);
  console.log(SIMapMov);
  var SIrandomSpeed = random(SIMapMax, SIMapMin);

  fill(200,175,50);
  ellipse(a, b, 30, 30);
  b = b + SIrandomSpeed;
  if (b > 500) {
    a = a + SIMapMov;
  }

  if(b > height*2) {
    a = 400; 
    b = 200;

  }
}

function randomPitch(){
  if (num >= 30) {
    fastball();
  } else {
    slider();
  }
  if (y > height || b > height){
  num;
}
text(num, 200, 200)
}