I really like this girl, but how to make her like me?

Hey,

sorry for the title as i didnt know how to put this story in 1 sentence.


Im 17 and There's a girl in my class and i have a crush on her for more than a year now.
Everytime we talk i get really nervous and i feel like im just saying stupid things.
Also im doing everything just to talk to her, like being really slow at the lockers
so that we leave school at the same time and talk a bit.

lets start at the beginning,
At first it was just like a normal crush, like i had more times, but it soon turned out this was way deeper,
i absoluty love everything about her and about everything she does and says.
But after like 3 months there was a party and i somehow slipped out to her that i really liked her. She
answered by saying she likes me as a friend, but nothing more. And somehow i justed bursted into tears and went home.
Then afterwards we spoke on msn about it and it gave me the idea the feelings for her were going away.
But the opposite seemed true, beacause my feelings were just coming back for her. Well then a few months passed,
with me just trying to act normally to her and say nice things, while inside my heart was beating like crazy.
then there was another party and she specially asked me to come, so I did as i want to grab every opportunity to be with her.
We were together for a very long time that eavening and then all of a sudden she started to make out with another dude.
I really felt heartbroken and went home crying once again.
Then through friends she found out what happened and she was saying sorry on msn, beacause"she didnt know i still had feelings for her" we spoke about it and once again i had the feeling for a week or so that it would go away. But that was not true, my feelings only became bigger and thats the point where im at now: Thinking she is the greatest person on the world, im doing everything i can to see her or speak to her, while she doesnt show that much interest in me. We still talk quite a lot at school, but i have the idea it always have to come from me. Apart from a few times at school she never starts the conversation.
However a few weeks ago i suddenly had the guts to ask her if she wanted to do something fun with me sometime.
She answered nor positive nor negative by saying that it would depend on what and when since she had some busy weeks upcoming. So we agreed to do it a few weeks later.
But now my problem is that i have no idea what to do next. When i see her and talk to her i feel really happy, but as soon as I cant see or speak to her anymore and have to wait for the next day of school, at that point im getting really sad and sometimes have to cry to. ( yes its that bad)
So should i somehow ask her again if she has time to do something fun or what? I just dont know and i hope you guys have some good advice and thanks for that in advance!
( my apologies for the bad english im dutch)