Sometimes I wonder when is the right time
To have sex.

When you are ready and don't have any doubts. The fact that you have to ask the question is already a doubt, which means you're not ready.

When you have a job, your own place to live and can afford to be a parent. So if you are mature enough to raise a child, then having sex would not be a issue

After marige

You need to wait until you are both physically, emotionally and financially ready to become a parent.

Even with proper protect there is still a chance of pregnancy as no contraception is 100%.

You need to be with someone you care about greatly and who feels the same for you. Trust me, don't let your first time be with some meaningless relationship that won't last (which is 90% of high school relationships)

I agree with everyone else. Also make sure you and your partner talk about what you would do if you were to become pregnant so that you're prepared and on the same page. Anything can happen.

Thank you ZoeMarie for the advice and everyone else.