I like what Araya had to say.

I've never thought of my self as bisexual, nor been sexually turned on by a woman. But a friendship with a woman became a bit more for me, started as a dare to kiss each other. Then we decided we liked it, got carried away and were sexually intimate. We then fell in love, and had a proper relationship. I left my boyfriend at the time to be with her.
This lasted about 6 months.
I'm now back with my boyfriend from earlier (Don't ask, it would appear to be a mess, but it's going well)

Anyway, I've never looked at another woman and been turned on by her. This was a relationship that stemmed from true love (So I believe anyway). Even though I'm with a guy now, I do not look at other woman and believe - wow, she is sexy, I'd like to make out with her.
So where does that leave me?
I do believe that the strict descriptions of straight, gay, bisexual... are really too limiting, as we all have different things going on in our heads and hearts.

The "funny" thing is that the woman I was involved with is bipolar, and used to have major mania spikes. I have since been dx'd bipolar, but have never experienced full mania. While our first experience may have been due to both of us having had a few drinks, and her possibly in a manic phase - this doesn't explain a relationship spanning 6 months...??!?!
Gosh, I've just managed to confuse myself!