Hi
If he put an app on your phone, that allows him to track you, you'll need to have someone look at your phone that knows what tracking programs look like. Look through your installed apps and see if anything sticks out obviously as a tracking app. I would suggest, that you take your phone to someone that has knowledge of these apps, because they do exist. Now, he would have had to have, physical contact with your phone, if that's possible, then I would suggest a certified person to look over your apps.
Hope this helps!
Chris