Tip: when you come to a pair of words with a slash, read the first word if you are female, the second if you are male.
Humor me for just a moment and follow me to a world that will never exist.
If you are currently a high school student, this will be easier, but if you are not, imagine yourself back in high school. This upside-down story works best for a boarding school, but could probably work for pulic/day schools too.
Imagine that you are the only openly straight student in your high school. You have a few straight teachers, but none to whom you feel particularly close. To the best of your knowledge, everyone around you is lesbian/gay. The girls are all hooking up with girls; the guys are all hooking up with guys. Because teen culture is still the same, the blushing confessions and cheering friends that mark a new relationship still happen all the time, but each new relationship is with a girl/guy. If you are a girl, the movie star posters in your friends' rooms all show Megan Foxx; if you are a guy, all the movie star posters show Zac Efron.
You never get asked to a dance because the girls/guys all want a romantic night out with their girlfriends/boyfriends and the boys/girls aren't attracted to you. Some boys/girls are uncomfortable dancing with you (even fast, group dances) because they aren't quite sure what you mean by it. Most people are aware of the fact that you are straight but many are uncomfortable with it; certainly you cannot discuss the ins and outs of your sexuality with just anyone and usually confine these kinds of topics to conversations with your closest friends. Some people think this is just a phase, and you'll grow out of it. Others say you'll come around in time and marry a woman/man, because after all that is God's wish as conveyed in scripture.
Get the picture? Here's the best part: keep your feelings for your current crush, boyfriend/girlfriend, or significant other the same, and imagine that he/she is dating his/her best friend of the same gender and has no romantic interest in you.
Sounds ridiculous when it's reversed like this, doesn't it?