when the playermp goes down the bar stays the same. shouldn't it be in step?
No, all drawing functions should be in the draw event.
Make sure the rest of your code is working properly and that variable is receiving change.
The draw event is much like the step event except it takes place after the step events and allows drawing functions to work, drawing functions ONLY work in this event, although if you choose not to use this event the object's sprite is still drawn.
If you want the object this is being drawn by to still be visible, include this in the draw event:
If your image scale, angle, opacity, or color is changed from the default value, use this instead: