I get sad everytime i see a beautifull girl

Hello all, i am 18 years old, I never really had a girlfriend yet. I don't have the best looks but i'm just really shy overall. But i kinda have an issue. (If you could call it that)

everytime i see a girl in real life (or on youtube) that i really like (Not only for looks), i always get this sad/depressed feeling inside. here's a bad example: I am dutch, so i usually get random dutch video's in my youtube feed. A week ago i got a video about a singing group ''og3ne''. I usually don't like the kind of girly music but they sang so good and i just got a huge crush on 1 of the girls, but everytime i see a video of them i get depressed. I get the same effect with every girl that i really like. (at school for example)

Everytime i get a crush on a girl i just get this feeling like, i can't be with her, but i want to. Even just as friends i just want to be close to her. But i know i can't. And everytime i hear someone say ''she's hot'' or some other useless comment i just wanna punch the dude in the face for being disrespectfull.

If anyone else has the same thing, i would like to know.

thanks a lot.