What do I do if I'm in a relationship with my best friend but then fall back in love with my ex girlfriend! :(

If you are feeling this way about your former girlfriend, then I suggest you go after that feeling,
They say you only fall in love once. Of course your best friend is your best friend, but if she really cares about you then she would want you to be happy. Go after this girl of yours before its too late!

Even if I started dating my best friend?

Well yes, if your best friend is your "best friend" she'd understand.

Okay thank you so much for replying;)

^ This ladyyyy knows what she talkingg about, haha(:
Well I meann, unless your ex girlfriendsss name happens to be Halley?
Pretty much the coolest girl in the world? Yeahh, I think so?(: