Help!!!!!!!

Basically I couldn't find her in the morning because I had a few things on my mind and I was late. At lunch I didn't see her either. After my second last period (spare) I was standing and just chatting with mt.biker by a class when she walks by, BY HER SELF. I flip out, but get nervous, biker being a good friend he is says a few words of encouragement and pushes me to go after. I follow, go up to her locker, she's standing with just one person, the one who has the locker beside her. So they are both talking, I go up to her and say "Hey, I always see you around the halls and I was just wondering if you would like to go see a movie (I ****ed up here lol, but oh well), play pool or just hang out and talk"
She looks at me with the most beautiful smile and says "Aaahhhhhhh, I'm really sorry but I already have a boyfriend"
"Oh, hmmmm, that's cool. Do you still want to just hang out and talk and just go play pool or something."
"Yeah sure."
"Can I get your number, or give you mine?"
"Best if you give me your number"
"Ok ummm do you have somewhere to write it"
"I actually cna't be late for next class and gotta run, I'm really sorrry again, but try to find me after school"

I did look but couldn't find her. I'll approach her tommorow just to give my number, but basically it's a no. She didn't reject me (hopefully) but said she's already seeing someone.

Why is it that every woman I really start to care for is either seeing someone, or sees me more as a friend or something. That's the too most "rejection" lines I got! I'm in my last months of grade 12 and I never dated yet.
This sucks....feeling kinda down. But I had a tlak with biker after. This is painful but I'm going to just STOP trying, I think, I hope.....boy I'm really confused.....