I was 17 at the time and so was my girlfriend. 100% true story.
About two years ago, I was going through a confusing time in my life and I thought I might have been bi. When I finally summoned the courage to talk to my girlfriend at the time about it, she was excited! I was amazed, but she was very sexual. She loved the idea of finding a guy to join us in our sexual endeavours.
Julie, my girlfriend at the time, usually loved to masturbate me all the time, she thought of it as a challenge to get me to cum. God I loved that! Well we couldn't think of a way to find a guy to join us without making my bi thoughts public knowledge, so we decided to try phallic objects. At first she lubed up her fingers and tried fingering my ass, adding more fingers as I instructed. Man was that hott! With one hand fingering my ass and her other hand jacking me off, I was in pleasureville!
She continued doing this for months and it ended up being the only thing that kept me away from actual dicks. Now I have a different girlfriend but I'm not bi or bi-curious anymore.
Hope you like my story!