It's difficult to relate to peoples sexuality, when it doesn't follow the same ruleset as your own.
I mean, I'm heterosexual, I can't relate to someone who is homosexual when it comes to sexuality. This should be no surprise, but then it shouldn't bother you either. Do you have to explain yourself to people?, maybe feeling a need to explain yourself is half the problem. If people are too narrow minded to see things from your perspective, then they're too narrow minded to offer any sort of advice, so avoid the subject of relationships with them, and talk about something else, it's not rocket surgery.
I know a lot of bisexual people, and people who are legitimately gay who have had girlfriends in the past. Is it society judging you, or you judging yourself by society's perceived standards. I tend to be quite secretive, I mean my last girlfriend never met any of my family or friends, to be honest I don't see what relevance other people have in relationships other than passing judgment... I found it refreshing to have a totally private relationship for once, fuck everybody else. I was able to figure out for myself that she was a fruit-bat.
Maybe your next relationship should be private, don't talk about it with your friends, don't arrange to go on nights out with their friends, for like the first couple of months at least. When your getting to know someone, avoid outside influences that might not be 100% in support of you or your relationship. Then by the time your friends or family do meet your partner, your relationship will already have a foothold, it won't be open for questioning, and if anyone does question it, tell them to piss off and mind their own business.