I had the moment you're having after I'd been married about 5 years. Then, I sat and discussed it at a theory with DH for another 4 years, before falling a bit for my best (girl) friend. That pushed the "poly discussion" into the realm of a real chat, and we've been at this chat about a month.
You can read about my take here
It's a rough and bumpy time, I hate to tell you, but what the people here will remind you is that you aren't necessarily going to be looking at a lifetime of repressing a bisexual nature OR a life without your DH. In the strictly mono world those are the two choices (well, that and cheating), but there are a wealth of different paths.
May I recommend two books?
The Ethical Slut (no, nobody is calling you a slut, it's just about how to handle more than one romantic/sexual relationship in an adult fashion)
Opening Up (it is like a beginner's primer for couples who find that they are faced with the possibility of opening their marriage)
I prefer the second book, but they are both helpful reads.