Thanks for query,
Sexual act has four stages.
Arousal,erection,Ejeculation & lag period.
You can increase the time between erection & ejeculation by start stop start technique.
As you are going to marry now your experience is of masturbation
There are vast difference between actual sex & masturbation.
So nothing to worry.no need to take any medicine as you have no disease.
This is a game between husband & wife daily so you can improve it on next day.
so relax & enjoy sex.