Learn to post code properly. Code is supposed to be pasted only after clicking the icon with the # sign on it.
Before copying code to past, use Tools + Auto Format to do proper indentation and make the code readable.
Some appropriate white space would be nice, too.
This this what I did to it. It turns on the motors in the proper direction but I want it to constantly read the buttons i press or it goes to default 2.5vs. Also on bootup it runs the motors uncontrollably until i hit 5 enter.
So, in setup(), replicate the code that is executed when the 5 is entered.
You need to do one of two things. Either change the application on the PC to something other than the Serial Monitor, to one that does something unnatural, or restructure the Arduino program to do something different only when the Arduino receives new serial data. That is, get rid of the else block.
Whatever you do, get rid of the damned Serial.flush() statement, unless YOU can explain exactly what it is doing and why you have it there.