The size of the penis will not come down because of mastrubation. It is just a psychological feeling that arises because you frequently involve in mastrubation and many time s you do it in a hurry or just for the sake of doing it rather than involve in it after you get enough interest and arousal. May be the fantacy thinking which you have been using may be becoming routine and boring because of which you may not be getting the necessary erection when you want to mastrubate. the fear anxiety and tension associated with losing your penis strength or having a neurological problem may be futher contributing to the lack of erection when you intend to mastrubate. Get over all the fears and invole in mastrubation only when you are aroused by approriate stimulus and not do it in a hurry or just because there is no other work to do. Also consult a Clinical psychologist at the earlist to get over these apprehensions

R.Manoj
Clinical Psychologist
rmanojcp@gmail.com