Hi,
Welcome to HCM.
First of all you need to relax a little bit. The antibiotic injection will not have these kind of effect. Secondly
masturbation is a way of sex, which even married people practice. You need not worry on the fact that you started masturbation early in your life or antibiotics.
Having said that your situation, circumstances and feelings are not clearly understood in your question.
I would like to know the following:
1. Do you watch porn? If yes, frequency and rough estimate of duration?
2. Do you smoke? If yes, frequency and number?
3. Do you drink? If yes, frequency and roughly the no. of drinks?
4. Do you use motorcycle? If Yes, since when, how long?
5. Are you under much pressure? (office/home/personal relations)
6. Are you sleep deprived?
7. Have you lost or gained weight in the last 2-3 months? and Please brief on your food habits.
If you clearly answer these questions, I can help you with this situation. It is not very serious, and easily treatable.