Guys: Have you ever seen a girl so hot that you get weak in the knees?

There is this girl at my college, she is so amazingly hot that I get weak in the knees every time I see her. Once I actually mustered up the courage to ask her to have lunch with me, and she did, but it turns out she had a boyfriend, so I backed off. but oh my god, have you ever seen a girl like this? she's so amazingly cute and beautiful...it's like i get breathless and get a bunch of energy at the same time and want to jump around, haha. is this normal?