dear friend Dont get worried..
is a common habbit in young age or adolescence group
As such it has no bad effect on health or fertilization but you know excess of every thing is bad.
Dont consider is as SIN or bad habbit as sayed by quacks or every drop of semen is equal to 100drops of blood, thats a common myth
Semen is regular body product or secretion like saliva, sweat
as your frequency is already reduced, dont worry ..
If you want to stop you can, divert your attention when you are alone, take few deep breaths, abstain from watching porn or erotic literature