Why do I feel this way?

I’m in a relationship, I think? We have been going out for 6 months and love eachother with everthing. But a couple days ago, she told me that our relationship is getting boring and that she’s breaking up with me. I didn’t know what to say I was so shocked. But I did say why, what can I do to make it better? She hung up. Then at about 4am she calls and tells me she loves me and made a mistake, I said I don’t know what I want to do, and that I love her. Today I told her that I just want a little time, to put our relationship on hold for a little bit, the get back with her. But as all this is going on, my best friends longtime girlfriend calls me and starts telling me that her, and my best friend are having trouble. So I try to help her the best I can, but a couple days ago, she told me that she likes me, and I began to like her too. I never liked someone so much, so fast. We have more in common then me and my girlfriend. We like eachother a lot and want to start dating, but think its to early because my girlfriend and her have issues together, and I don’t want to lose a friend. What should I do?