All I can tell you is that if you are correctly classified as exempt, and I cannot say that you are or aren't with the information available, there are no circumstances whatsoever under which you are entitled to a single penny of overtime no matter how many or how few hours you work, or are on call. That is exactly what exempt means - that you are exempt from overtime.
The above presumes that you do not have a legally binding contract that expressly says otherwise.

