Then it seems like the type of situation that needs time to get better. You probably got it covered then.

Explain what you said to us to your boyfriend. He can't read your mind, but you can speak yours. You show him your perspective and that won't give him much room to doubt himself in this situation.

Assumptions really are the mother of all fuckups and you don't want him assuming shit because you're both 18 and your brains aren't fully developed yet, so you're both likely to fuck up at that point.