Bisexual and conflicted

I never understood I was bi until I was an adult. I was raised very conservative and definitely liked boys so I never considered that I might be gay.  I realized it when I was 19, but didn't come out-or even fully embrace it-until I was 23.  I've never been with a girl or even more than a simple kiss.  It's been bothering me a lot lately, and I don't know if it's just the curiosity or lust or what. The problem is, I'm already married and a mum.  I love my husband very much and I'm happy, so I don't know where these feelings are stemming from.  After confessing my feelings to my husband, he was supportive and said he is not open to a threesome but would be okay if I expiramented with a girl if it meant giving me closure to how I was feeling. I can't say I don't want to be with a girl, but I don't know if having sex with a girl would help me feel better or just cause worse feelings or problems in my marriage. I don't even know where I would find a girl willing to expirament with me! 

I don't know what to do. I feel sad and I don't know why. I can't stop thinking about it.  I guess I'm just hoping someone else has felt this way, and can give me advice on what to do.  I know maybe a handful of gay/bi girls, so I feel really alone in this. :(