Need hlp regarding masturbation?

I m 17 yr old guy prprng for engnrg xam but i used to masturbate 2 or 3 times a month but i m trying to stop tha frm pas 3 weeks i hav nt masturbated nd nt watched but nw its vry difficult to stop frm nd masturbation....While studying also i think abt nd .....Plz hlp me to cntrl ol dis