I was at a party with my boyfriend.
We were outside though.
And in the dream, we crossed a bridge (one of those older slightly rickety ones) to get to the house.

Then the dream changes.
He's left me at the party, because he had to run a friend somewhere quickly.
Then I meet this girl there.
And we sneak into the bathroom together.
We start to act intimate.
In fact, it's sort of reenacting something that had happened earlier the previous day to me in real life.
(I won't go into detail, but my boyfriend and I were jokingly acting like the opposite gender)
Then two girls open the doors and say "Oh, I knew there was some lezzy action going on in here"
Of course, I don't pay much attention though, because I don't really care what they think.
I just basically tell them to shove it and get a life.


Then I wake up.

No, I've never questioned my sexuality.

I think it's just your unconscious mind wondering "what if". It doesn't mean you actually want or plan to have a same-sex encounter in waking life.

Since you were both pretending to be the opposite sex, then maybe your unconscious just went the next step and asked, "What if instead of being with someone who is pretending to be a woman, I was really with a woman?"

Your dreams provide you with an opportunity to try things that you would never do in your waking life.

The bridge could represent the path to your unconscious mind (where you are free to experiment with things like lesbianism). The two girls sound like they are the parts of you that are still aware that this isn't right for you, trying to force your waking-life restrictions onto your dream life.