[M] How I became a bisexual

So it all started when I was a young teenager (now 38m) and I had a very promiscuous and adventurous girlfriend. I’ve always been very open minded sexually, however I considered myself to be heterosexual. My girlfriend at the time seamed to be far more experimental and confident when it came to her sexuality than me. She was bisexual, into assplay, pegging and MMF, anything kinky really. So most times during sex together she would try “assplay” on me, however at that time I had never done it and I wasnt that comfortable with the idea, untill….
…One night we were at her house drinking and doing ecstasy together. We started some hot & heavy sex and next thing I know she had her vibrator inside me and she was really going for it lol. Woh, I wasn’t sure at first but I could see how much it was turning her on so I thought, fuck it! I completely surrendered and let her do what she wanted to me. Once I relaxed… omg I was in total HEAVEN!! I couldn’t believe that I’d been missing out on this feeling. Gosh, I wanted this feeling more and more. Obviously from this point onwards my views on assplay changed, we would do it all the time. I no longer felt any stigma towards it, I actually fell in love with the pleasure. And on-top of that I began to have other feelings, I felt that there could potentially be something else going on sexually with me, I didn’t know exactly what that was at the time, but I’m definitely excited and nervous to find out. This girl was my first love and I fell so deeply in love with her. But, unfortunately the relationship only lasted a few years. I didn’t know it yet but that relationship would kickstart the beginning of my sexual journey.