I don't think you should be in a rush to label yourself. You might be 100% gay, or you might be 100% straight....or you might be anywhere along that scale.
For example, an ex of mine was obviously at least straight enough to enjoy sex with a man (me!) but she also fantasised about women regularly too. It confused her a lot because, like you, she was concerned with what it meant. I helped her see it doesn't matter what it means, you just go with the flow and she was a lot happier, as was I.
I think there's probably a difference between fantasy lesbianism and reality anyway, as some couldn't actually go through with it. Also, in my case (well, the gf's) whilst she could (happily) imagine sex with a woman, she couldn't imagine being in love or in a relationship with one. The point is though, it didn't matter, you can still get what you want without labelling yourself either way.
Just go with what you feel at the time, even if that changes day to day. Don't worry about giving yourself a category, you don't need to explain yourself to anyone.