I don't know what to do with myself. Need girlfriend/relationship advice desperately?

I've been dating the same girl for about 5 months. She asked me out and I liked her so I said yes. But I don't think our relationship has grown. During the week I feel kinda rugged and I can't stand walking in the school hallways with her, but on the weekends we have great times. It's kinda like I have two girlfriends. One who is really clingy and moody during the week and one who is relaxed and calm during the weekend. I've been going through this pattern for a pretty long time, and my feelings are so conflicted I can't tell whether or not I love her. I tried to break up with her a few weeks ago, but she hinted at committing suicide and I felt so guilty that I don't love her as much as she loves me that I gave in and didn't break up with her. The whole thing got worse when one of my other friends instigated a forced discussion of everything in school during the week, which ended in a breakup...for like a few hours. She wrote me this really sad note, and I gave in again. I've been trying to make things work, but I don't think that I love her, still. She really loves me and is really clingy. I'm her first major, long-term relationship, and I've never been in any relationship before. I really don't want to hurt her. Plus, I've taken flak from a lot of people in my school for trying to break it off. I get dirty looks all the time, and it's really painful. To add to the terrible mix, I think I'm falling in love with someone else. Nobody knows how I feel about this other girl, but it kinda hurts when I see her because my heart beats faster and I lose my breathe, but at the same time when I see my girlfriend my heart bleeds because I know if I end our relationship she won't really have a close friend. I'm also worried that she won't be able to get past the breakup because she sees it as being the end to her meaningful life and that it can only go downhill from there. There's plenty more, but I don't think it's relevant, or appropriate to share. But basically, FML. I could really use some solid advice. I know I've gotten myself into a really tough mess, and I don't need anybody telling me that, but I wanna know how I can get out of the mess while hurting the fewest people possible. I need somebody to help me get past my own screwed up emotionsI don't know what to do with myself. Need girlfriend/relationship advice desperately?
From personal experience, the longer you hold off breaking up, the worse it will get. You both need to realize that you will have more than one serious relationship in life. First loves rarely last for too long. Also, since you like this other girl, it's obvious that your girlfriend isn't ';the one.'; As difficult as it may seem, breaking up with her now will make things better and easier for everyone in the long run. As for her hinting at suicide if you break up with her: 1) she should seriously attend counseling, even if it's just with the school counselor, and 2) when someone threatens suicide if you break up with them, it is a sign of emotional abuse; she is trying to control you. Please think about this.I don't know what to do with myself. Need girlfriend/relationship advice desperately?
This is really straight but if you dont like her or dont love her then dont waste your time or hers. It wont work out in the long run if you cant love her all the time. But i wouldnt break up with her and turn around and go out with someone else right away either, you would have to give her some time to heal first.