am I doing it vainly ? does it have side effects or is it somehow harmful ?
No, it is not in vain. Any exercise is better than no exercise, and you should keep doing it whenever you can.
Also in the morning when i begin a jogging session i feel like an inner body reaction that provokes me to throw up, is it due to something grass i eat at night ?
I don't know what you mean here. Do you eat grass in the evenings?
and what is the proper diet to prevent this ?
There is no single diet that resolves all your problems. If you have problems with recurring nausea, you should see a doctor.
For now, make sure you don't run for at least a half hour after a meal. And if you still get sick, try eating something else, but keep it healthy.