I’m starting to accept myself as bisexual and I have a boyfriend of 6 years and he is very open to me exploring my feelings for girls…but if I find one he will want me to share her with him otherwise he will feel left out, I feel like it’s going to be very hard for me to find a girl friend who will be understanding of the situation. I’m not really sure what to do…

People are not things to be “shared.” There is really no situation in which you can require someone to get romantically or sexually involved with someone else, or just assume that they will. If a girl likes you and is into you, there is NO guarantee that she will also like and be into your boyfriend. Having that as a prerequisite for dating someone limits your options severely - think about how hard it is to find someone who likes you+you like them - now you have to find someone who likes you+you like them+they like your boyfriend+your boyfriend likes them. So you are very correct that it will be hard to find someone who will be “understanding.”

Talk to your boyfriend about why he has this as a requirement, and what you two can do to address it. If he just feels “left out,” why not open up your relationship on both sides, so he can pursue other partners as well? Does he see this as a mostly sexual thing, like finding someone to have threesomes with, rather than you finding someone to explore your feelings with? There are other ways to help your boyfriend feel comfortable with this besides setting unrealistic expectations for a mythical person who will be equally interested in both of you.