WHERE IS THIS FREAKING TRACKING DEVICE IN MY CAR? He always knows where I am?

I have had enough of my soon to be ex husband knowing everything about what I'm doing. I KNOW for a fact there is a tracking device on my car (not on my phone) because we owned a car lot and he used to put them in higher priced cars we'd lease. I just don't know for the life of me where it is. I know it isn't one from the outside, it isn't by the exhaust, or under the hood. WHERE COULD IT BE?!?!? Freaking driving me nuts. He always knows the cross streets where I am but never the actual building I'm at.