The time to do anything is when you want to.
It is not unusual for young males to be sexually selfish. Some have way less empathy than physical hunger...some are simply seeing every new thing as part a rite of passage, as if it will get them to their mature masculinity more quickly.
On the other hand, whatever anyone tells you about any part of sex is, likely as not, what they tell themselves to avoid new experiences, or being judged for being 'different' or 'ewwwww!'.....although some reports from folks who have tried it out (liking it or not) are as likely to be honest as not.
The best information is what your own desire and body tell you. If you are curious about it, look for stories about people who took their time and found out that they did, or didn't like it. Decide if you want to try some preparatory steps and self-play, so that you can get more familiar with your feelings, and see if any desire awakens.
If you don't discover curiosity and desire for it, then 'just doing it' would only be to serve someone else's curiosity and desire. Is that the kind of relationship you want ?
Then there is relationship-economics: if he is not empathetic, or equally interested in your feelings as your body, or supportive of you having power over your own life and body, then this is not going to be a lasting relationship. If so, you may want to limit your risks and investments in it.
If you are a no, then say no.
If you are a 'not now', say not now.
If he demands an explanation, or keeps prying, then that is bad.
If you are afraid of him withdrawing, or going away, or anything that would make you betray your own desires and self-control, then this is an opportunity to build your character.
When you sense you may betray yourself, that is the time to face these fears, get moral/emotional support, and draw courage from role-models and advisors and stand your ground.
Facing the risk of abandonment in order to keep your self-respect will be a major building block of your self-love and your power to help yourself and others.
I hope (at least)parts of this have been helpful.