It is not possible for me to give you the perfect answer. You have to decide yourself what you'll do in this situation.
Making out with another guy is not such a huge deal. But because you did that, you need to rethink what your boyfriend means to you. You aren't happy with him for the full 100%, Or else you wouldn't make out with another guy.
You are way too young to be worrying, or thinking about what you have done. You are not married yet, so you have all the freedom in the world to do whatever you want but- Your own morals and consiousness will probaly help you think otherwise.
If this happens more often that it should, then I'd think its for the best if you tell him the truth. He deserves that. But if you are truly regretting what you did and know you won't do it ever again, why laying that out on the table? Everyone makes mistakes, but it is up to you if you will let that one mistake ruin your relationship or not.
And with those hormones running through your body, it is bound to happen to feel like flirting and making out- even if its not your boyfriend. It is your ex, and it is only logical that you see only his good sides in the heat of the moment. But still, if you think as it of something that could happen more often, well, the it's probaly for the best to end your relationship before he does when he finds out. And that, will make thinks only worse.
I hope I have been of some assistance.
Good luck, and keep us posted!!
Kind Regards of Rapunzel.
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