Do not give too much importance to masturbation becoz at this age it is pretty common.If you think your body is becoming uncomfortable due this activity , try reduce the frequency of masturbation.
I can't tell anymore because to leave this addiction you must go outside and play and get involved in some work. Hope this helps
No this most biggest mistake people do that they take medicine for this small problem. As per it is not at all a problem. But as you have your mbbs admission I recommend you that after masturbation be normal and don't give it importance. Some people go to depression after this act. I would tell don't take any medicine as it can cause a future problem in your married life. Stay happy and be normal. I am sure that after the age of 20 your frequency of masturbation will automatically decrease