The tricky thing about talking about phases when it comes to sexual orientation is that, for plenty of people, sexual orientation is a fluid thing, one that changes over the course of their life, while for others it's something that feels very unchanging. Someone who finds their orientation changing over their life could very well be said to have "phases." But just because something is a phase doesn't mean it wasn't or isn't real, or that the person was "faking" what they felt. It just means that they had information that lead them to identify one way, then they got new information about themselves as they moved through life. Does that make sense?
Too, you don't necessarily need to experience a sexual encounter in order to confirm or prove your orientation, for a few reasons. First, you mention that the times you've kissed girls have been laughed off, but on your end it sounds like you actually enjoyed the moment and were attracted to the girls you kissed. Both those things are indicators that you're attracted to women. And second, sexual orientation is about attraction more than action. For a variety of reasons, someone could realize they're a different orientation than they thought but choose not to act on those feelings. After all, we take people at their word that they're straight even if they've yet to have sex with a person of a different gender; queer identities are the same way.
If you're needing help sorting out your feelings around your orientation for yourself, I really like the questions included in this article to help people explore what their orientation might be: The Rainbow Connection: Orientation for Everyone