Any advice for coming out as bi when you’re in a long term heterosexual relationship?

Hi, I’m a 37 year old man and finally accepted that I am bisexual over the last few months. I have felt attracted to men since I was 15 but mostly suppressed it and have been in a relationship with a woman for the last 12 years.

I love my partner and genuinely want to stay with her. However I also can’t ignore this side of myself and can’t be happy if I carry on suppressing it. If I’m completely honest I am attracted to women but would probably be more likely to pursue a sexual relationship with a man if I was single right now. I have no intention whatsoever to cheat on my partner but also want to be honest about who I am and not have to fear that I will somehow give myself away at some point.

I don’t want to do anything rash but also wondering if anyone has any advice or has been in a similar situation? How can I start this conversation with my partner? My mental health is suffering because of this and I don’t think this situation can carry on long term.

Thanks