Is it bad to run on my toes ? instead of the heels ?

It can be: It is necessary when wearing minimalist shoes. You need to build your muscle tone gradually to prevent muscle strain or injury.

Running: This relates to 2 different types of running. Short distance or sprinting is done entirely on the toes. Running heel to toe is usually reserved for longer and long distance running. So , it depends on what you are training for . Interval training using different distances will allow you to balance training as well as let you find your optimal distance for competition.