Need some general advice on everyone's favorite topic. Girls.

Not really sure what to do, and I can't really talk to people I know because they either know the parties involved, or they just brush it off to me being a man-whore.
This is really long, but if you just want to here the basic gist, skip to the fun part.
Here's the back story.
I dated a girl on and off for a few years and we ended up breaking up a few months after we switched coasts and we stopped talking. This was partially due to sobriety (her goal) and infedelity on her part because while I had cut back a lot, she stopped completely and was going to meetings. (For an example of cutting back, in the last 5 months of our relationship, I drank 3 times ever and only got drunk one of those times [after she cheated]. The other two times were a friend's birthday where I had one beer, and when some friends visted me from Cali and I had two beers)
We stopped talking for a few months, then when she found out my dad died, she came across the country to see me in CA. Then we were together for a few weeks after and ended again. Stopped talking again, and then recently started talking in Feb.
The Chase:
So she needed help with her essay for school, so in exchange she drove me up to CVS to buy some wrappers (Remember to wrap it before you tap it -Grandpa) and then cleaned my house so I could have a girl over the next day and not be worried about the mess of ashtrays and beer bottles. This was a Tuesday.
The girl from my class spent 2 days at my house and on Friday I saw my ex again and we ended up doing it. Then this happened a few more times and we started dating again for maybe a few weeks.
It was great. She was a lot nicer, we communicated, all that good stuff. She didn't care if I smoked or drank so long as I gave her a heads up so she could decide if she wanted to be around me. She finally realized that not everyone who drinks is an alcoholic.
Yet despite it all, my heart wasn't in it, but I was comfortable.
The Conclusion:
So this past weekend was my friend's birthday party. There is this other girl from my school, who I think is awesome. We both got really comfortable really quickly with eachother but it never went anywhere. I liked her, she liked me, all that fun stuff, but it never seemed to line up right.
We ended up hooking up though on a beer run, and then slept together later that night. So I effectively cheated on my (ex)girlfriend and I broke up with her that Sunday. She was pretty upset.
I've never cheated on a girl before (mainly because I really don't do relationships) so I felt terrible, plus I really liked this other girl a lot. I didn't tell my now ex-girlfriend, I just said that I wasn't happy etc. I couldn't in good conscious be with her when I had feelings for someone else (coincidently, the other girl is only the second girl I've had feelings for)
The Fun Part
The girl who was in my class from awhile ago hates me, because her friend was at the party where I slept with that other girl. Its a shame because she's such a good friend, and I want to maintain at least something of that.
The exgirlfriend, I found out last night, tried to kill herself and is currently in the hospital. I feel terrible about this and now while I have this thing on my chest I don't think I could ever rightly get it off. I don't want to hurt her feelings (too late) and I just want her to be happy and get on with her life. I still love her, but I'm not in love with her. I would like to, if I'm able, still be her friend because we have such a history together. (We've known eachother since I was 4 years old)
The girl I like's exboyfriend apparently tried to do the same thing as my ex over the weekend though it hasn't been confirmed. She feels guilty about that, but I can't convince her that its not her fault. She also feels upset still about her exboyfriend and kind of bitter. Our mutual friend said that she doesn't have any closure. The girl told me today that she couldn't do anything right now, as much as she wants to, because she doesn't want to take things out on me for what he did, and she doesn't want to drag me into it either.
So TB, what have I gotten myself into? Any advice on how to extricate myself from this **** storm with the most minimal amount of damage to all parties involved?