Hey there Wittians

So, I like a boy... Typical story.... He likes a different girl and I get a broken heart blah blah blah.
Well, yeah, he likes a different girl and that girl is my (ex-)BFF (He just won't admit it). So far I don't have a THAT much of a broken heart but here's the thing. My friend (not the one he likes) and I like to spend break with him when we can (He's really quiet and usually spends break with himself). We like to just play game like just try and snag his cap and we poke him and stuff like that. But now he hits us with his lunchbox and his hands. But then one day we apparently went to far and he hit me so hard I had (I'm still wearing it) for 2 months (It's my 1st month). I told everyone that I fell off a tree but only him, my friend and I know the truth. Just yesterday he wrote a note and put it in my desk and it said:

"(my name)....I'm so sorry. I didn't mean to hurt you that much. I didn't think you would need to get a cast. That's the last thing I thought you would get. I don't want anything to happen to you, (my name).... From: (his name)"

Now today, to make it EVEN better, I found him making out with my (ex-)BFF. I started to cry right there on the spot and my (ex-)BFF finally broke away and ran up to me and tried to hug me but I pushed her away. I said through tears that I couldn't believe she would do this to me.

What should I do? How can I go to school tomorrow and face them? Please give me some advice.