Is it normal to always get a crush on a girl that is currently dating?

Never rub another man's rhubarb.

Wait...what does liking a girl have to do with fighting people? We're human beings, not bonobos. We don't have to indulge in threat displays and ritual mating behaviors like other primates. Women are not property to be won in a fight and dragged off by the hair.

You have weird definitions of liking people if it gets you beaten up.

Try interacting with women as people. They may start to choose you of their own accord, and you won't have to pound your chest and throw feces to claim your right to mount her or whatever weird courtship thing you think you're doing.

It's quite normal to want the one you can't have. Human beings produce a chemical called "pheromones". Many times you hear the term when women talk about their period. Pheromones are produced naturally off of our bodies, and spread through the air. Women that spend a lot of time together tend to get on similar cycles because of these chemicals.

However, both women and men produce these chemicals. This chemical is a natural scent that people have them makes us feel more attracted to them. That's why many cologne and perfume companies will advertise, "Our product has pheromones in it!" (Btw, no it doesn't... you can put pheromones into a product, however, the pheromones are masked by the product and negate the natural effect of pheromones.) It's not something we can always smell, but it's the reason why some people are into sniffing other people's underwear. They are aroused by the pheromones that come from the natural body. The more you shave your body hair and mask your body with cologne and perfume, the less pheromones are being produced.

However, there is a loophole. Many people have studied that the more confident someone is, the more pheromones they will produce. So if wearing cologne or perfume makes you feel more confident, than it could benefit you and produce more pheromones. So being popular, pretty, and having a jock boyfriend would certainly boost her confidence and ultimately make her more attractive to people. This can happen with anyone in a relationship. When you're glad to have someone special in your life, you start to produce more and more pheromones. I make the joke that potential love interests don't come one at a time, they come in waves. Because once I have a boyfriend, almost like magic, every boy starts to give me more attention, smiling at me, etc.

Anyways, sorry for the long explanation, I wish you luck with your situation. But now you might understand why there is some normalcy to "wanting the one you can't have".

Normal. The fighting is a bit on the exaggeration side. As for always wanting that girl, obviously she looks great so you're not the only one. I'm sure if you stop looking at your life like it's a movie, you'd be ok to talk to anyone When I was in school, I talked to ANYONE I wanted to and laughed with and at everyone. There's no such thing as popular, nerds, jocks, etc. You and your peers are copying movies and tv shows. You just have to remember to not get caught by their boyfriends. Keep the conversations short. The next day, keep it short but the last sentence should be something around the fact that it'd be cool to hang out with her. Ask for the number then, or wait till the next day but either way let that be the last thing. Something that'll keep her thinking about it after school. School girls LOVE to think about school when they're at home. After all, that's pretty much all of your lives. That's why there's no such thing as popular. And always talk to more than one girl. Your choice to keep it friendly, but she sees that you have more options.

Maybe you have an unconscious fear of intimacy so you are attracted to girls who are unavailable. Then you punish yourself by getting in fights with their boyfriends. Not to sounds like Sigmund Freud but I'm curious about what kind of relationship you have with your mother. Is she smothering or perhaps a little distant? Is your father domineering and authoritarian perhaps?

If she wanted you, she would be with you.

Logic dumbass, try it.

You need to level up motherfucker.