Masturbation - why it's led me to question my sexual identity

I initially posted this yesterday but felt i had to add more background. Two weeks ago my partner opened my laptop and found chat rooms and direct chats that I had not closed of a very explicit sexual nature between me and another man. She was and is understandably hurt and angry, accusing me of cheating, and being bi or gay. I hold my hands up to this i had never thought of online masturbating and cybersex as cheating until now and I fully accept that it is. I still struggle with the question of am I gay or bi - gay definitely not but bi maybe yes. All my sexual activities with men have been online only.

Why do I masturbate??

I like many started to give self relief as a teenager using soft core pornographic magazine's. As i got older internet porn became a more discreet and easy way to access porn when i was between relationships and became a normal part of my life. As the physical side of our relationship ended i again turned to soft porn but also started to use chat rooms as an alternative - always the same room on the same chat network where i would login as a guest frequently changing my name and never giving my true identity or location. I read the comments but initially did not interact directly. The room is mostly guys and i suspect some of the women were guys, often i would get a dm from a guy asking if i was gay or bi or would them playing as a woman be ok - i would answer politely and close the dm. As my use went on i accepted one guy to play a straight scene with him as the woman even though i knew it was a guy i still got the relief i needed as i masturbated during the chat session. Going on i started accepting and initiating more obviously gay themed chats - roleplay mostly and also latterly more full on gay sex scenes that gave me the outlet i needed.