Thoughts on being bi-sexual

I'm 25 years old and for as long as I can remember I've always like both men and woman. I've had girlfriends and boyfriends but I'm currently with my boyfriend of 4 years who I love. My problem is, people don't identify me as bi because I have a boyfriend. They say it's not real and they must think I'm lieing or something? Just because I'm not with a girl does not mean my girl liking side is gone. Like if a straight person is dateing someone of the.opposite sex that does not mean they stop liking all other opposite sexes. Were only human. I can be in love with my guy but still see other woman and men and think they are attractive. That's just what humans do. That doesn't mean I'm going to cheat on my boyfriend with a girl but it also doesn't mean I'm magically turned straight either. How does everyone else feel about bi-sexuality?