Sometimes people tell us things without talking.
You two have been together since you were 13! It looks to me like your boyfriend wants to break up so he can explore other relationships before he settles down. Instead of being honest with you (and maybe with himself) about it, he sets up situations where you will catch him looking around. He is willing to be the “bad guy,” so you can be the one to break it off and perhaps spare your feelings a bit.
You aren’t taking him up on it, which must make him feel both frustrated and upset.
Please do — take him up on it, that is. Break this off and get more experience with relationships. After you’ve been apart for a while and have seen who else is out there, you two might find each other again. If that happens, you’ll be on much more secure footing for a permanent commitment. If it doesn’t, my hope is that you will each have discovered a more mature and lasting love.
I wish you well.