When you are fouling it is usually a symptom of fast feet. Check your tempo, it shouldn't be faster than your normal walking gate.
To check your speed, you can do this before they turn the lanes on, stand in your normal starting stance and place the ball in the middle of your belly, then walk toward the foul line. If you feel like you want to go faster than your normal walking speed then you are going too fast. Repeat this until you feel comfortable walking with the ball in your belly, then throw a shot using the same speed. This will take some time to get used to so be patient.