Yeh, you probably will want to have sex outside of the relationship. You're 19, after sometime you will probably want more experience. I guess you have to ask yourself if you are a strong enough man not to submit to your urges? take the cue from that answer.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~