Cursometer | jQuery plug-in for capturing cursor speed | Plugin library

(Firstly, let me say that the code for this is in my github repo: Click Here)

The repo should give you all the clues necessary to what the issue is, however if you were to open up the index.html file and click, a counter should start in the top left corner. It seems to work perfectly for a bit, however if you click a lot and drag the mouse and move it around the page for a bit, the counter suddenly goes insane and counting rapidly.

I can't find where the issue is with the code doing this; I gave setInterval() a specific time to update timer, however after moving the mouse, a bunch of clicks, and dragging the mouse, etc...the counter goes crazy. Normally it wouldn't be too bad of an issue, however the site I am implementing this on requires a lot of clicks and mouse movement.

My next issue is that I cannot find a way to stop counting on mouseup. At the moment, when mouse is down OR up, the counter count. However, I want it to start counting when left-click is held, and stop when I take my finger off left click. I've tried a while loop like while (mouseDown === true) ... and that just doesn't load the page correctly.

Any help is appreciated!