May be you are very young in the business. Since it is not fair to know your age may I advise that as you get older you will have to notice that it is taking much time.
You can not just have your first sex and last for half an hour to cam. It is also a profession to last longer before you actually cam. It requires experiences and responsibilities to go longer and not an easy task for older age where every nut is tight!
It is not easy for you to conceptualise by now but you will appreciate it after a while.
Everyone when a boy faced the same when committing adultery; and it was due to many factors and it sis for you that; its a sin, its someone's wife, someone's girl friend, like that you will be caught, and you tend o make it last shorter and at the end you feel like unsatisfied you go back and find that you can not do it and dont feel like doing it cause your mind what why did I cam so quick. Other factor is may be you wife pussy is so tight that you get an ernomous friction for you to come so quick.
BUT SIO TATIZO NI TIME FUNCTION TU Ucjali bwana mdogo!
Cheers!