An interesting question. I knew I was different at a very early age. As I grew older and became a teenager, I found myself attracted to both girls and boys. I eventually had a steady girlfriend whom I had known for years, but I couldn't help but feel some attraction to boys. Like you, I too eventually had my first experience with a guy I knew for years. Like you, I won't go into details. Over the years I have had other encounters. I've been married for many years now. I'm still attracted to both sexes. So, I'm quite certain I am bi and have been from a very early age. Now that I am again on the rollercoaster, I'm waiting to see what will happen next as I begin my gradual transition to being me.