Alice,
That had to be hard for you. It's tough enough to be out in public for a long time, and all the nervous worries that brings. Add the fact that your 2 best friends, one which you liked as more than a friend, hooked up, which brings all kinds of emotions, most of which aren't wonderful. No wonder you broke down...bless your heart. Your friends sound like nice people who understand that all of us have our moments of being overwhealmed, and won't hold it against you.
It is obvious they both still want you as a friend. It may be a little awkward at times, but don't cut yourself off from your friends just because they are together. OK, the kissing and such will be hard to take, but if it lasts, you will miss both of them. If it doesn't, you may have to visit them separately, but that wouldn' be so bad now, would it?
So you were shocked while already in a stressful state. Stuff happens. You still have some weekend left so forgive yourself (you would them, right?) and get on with your life. It would be understandable it you decide not to hang out with your friends for a couple of weeks or so, (and that could be tough for you), but at least you can talk to them on the phone.
Take care of yourself. All of us here will be thinking about you.
Big Hug......Laurie