First of all remove all myths & misconceptions from your mind about masturbation
In fact, Masturbation is completely normal & doesn't have any bad effect to the body and mind.
So...don't worry about all this & stay relaxed
..this helps in improving concentration & builds up the confidence level.
Health can be improved by having a diet rich in fruits, vegetables, fish, nuts & honey.
One more thing...avoid consuming any over the counter medication
which claim to increase the size of penis or improve performance...it may be harmful.
Best thing is to eat a healthy diet, exercise regularly, avoid stress, get good sleep, think positive and stay happy.
Wishing you a Healthy Life.