oh gosh, if any of that's true poor you omg
Literally if you fancy a girl find an excuse to talk to her, drop your pen near her or something, ANYTHING. The most important part is to actually take note of her reaction to you talking to her, does she seem to want to talk to you?? If yes just try it again maybe, but not too pushy, just the odd chat here and there, if she fancies you you should know soon enough (although boys struggle with that too-a whole other story that though)
If she's clearly not interested don't be a moody lil *****-talk to someone else. No one likes a sad miserable loner. Harsh but true.
Now go forth and pull-you'll probs succeed at some point.