I have been through so many heart breaks so I can relate. A broken heart is the worst pain I have ever felt. I am 48 though but still can remember the high school heart breaks I had.

Guys at the high school age are just so much more immature than girls. I know this from personal experience and also I have an 18 year old daughter.

It does sound to me like maybe there is someone else in his life.
It is most likely nothing that you did or said at all.

I wish I could help more. I can relate so much to your situation. Unfortunately men do not get any easier to figure out as you get older. My husband left me after 17 years of marriage for an old college girlfriend. I have been dating off and on since and actually the men seem MORE immature at my age!

You need a hug! Hope he lets you know what is going on.