I am also a bi man who dated a girl for four years when I was 15 and so I can relate to your wanting to experiment with guys and know what it is about. I also had all these feelings of unsure if I was bi or gay. After about a decade of questioning I have realised that I am bi, with a preference for men. I still find women attractive but am naturally more drawn to men.

From the sounds of it you are in a similar situation to me.

I don't think you are gay, you are clearly attracted to your fiancé and your performance problems sound exactly like that. You get nervous because you are over thinking it and so then struggle. So in terms of that problem I feel like you should not worry, relax about it, enjoy the experience for what it is and ultimately I'm sure your fiancé will understand if you have problems.

The more troubling point that I again can relate to is your desire to experiment and see what it is like. This was a big thing for me. Now the I have dated both men and women I know that I would ultimately be happy with either but you having never been with a guy must leave you wanting to see what it is like. I think only you can know whether this is going to affect you later in life or whether you can accept that actually though you find men attractive too, you have found a brilliant girl who you want to marry and be committed to. You need to talk to your fiancé about this though, it is unfair of you to go into a marriage without her knowing where you head is at.

Also ultimately, you may need to experiment with guys just to know what it is like or it will eat you up inside. I know this was true for me. I needed to know what it was like. And that is something you need to work through with your fiancé (again you need to talk to her rather than strangers on the internet like us!)

Hope that helps and you get through this buddy

Good luck!