Thanks for query,
There are four stages of sex.
Arousal,Erection,Ejeculation & lag period.
Once you gets ejeculation the lag period starts.
It last for 2-3 hours in young to 3-4 days in older.
You get weak arousal or no arousal when you are in this period.
As you masturbate whole night this happens.
Remember excess is always poison.
so limit your masturbation
act by diverting your mind in other activity.
You will be better.