Does this look sincere?

Okay so two weeks 前 I broke up withy bf of 3 months.
It was great for first couple weeks, although we lived far away we saw each other every 日 during three days of college a week.

But we drifted away as he became withdrawn from me for some reason... And soon started hanging out with his female friend more.

I got so stressed that in the end we arranged to break up and then he dropped me like a ton of bricks and acted like everything we had didn't mean shit to him.

Angry, hurt, and confused, I confided in some the other people in my class, 発言しました a few things I shouldn't have.
I have been 芝居 like a 雌犬 towards the other girl によって giving her looks and stuff (immature, I know.)
And now I just feel bad because he knows that I spoke behind his back. I realise after clearing my head that I should have been もっと見る mature about it.
But now I don't know what to do anymore. We haven't been on speaking terms since. I feel awful :(

It is very unlikely we will be ever getting back together または will be close friends, but I want to have the decency to admit that I was wrong.

Seeing as it would be too awkward to say this to him in person, should i フェイスブック him this? If so, when?
Thank あなた to whoever can help x