Life can be a painful business, especially when you are young. I remember what it was like and you have my sympathy...
My old mother used to have a saying (proverb) she used to cover all sorts of disappointments and disasters - "everything happens for the best"...
I used to think "thats stupid, what did she know about what I was feeling"...
Strangely, mum was usually right and what I had seen as something bad did usually turn out right in the end - I should have had more faith!
It won't help you now but you must take comfort where you can - any boy who doesn't notice you or is ill-mannered enough not to care is not really worth bothering with!
Until your crush, or infatuation, or love for the boy passes and is replaced by another that will, hopefully, be returned next time (because there will be a next time and perhaps many "next times") you must keep in mind the fact that almost every human that ever lived and will ever live has gone through and felt what you are going through and feeling now...
Surprisingly, it didn't harm them and even more surprisingly the sky didn't fall and it didn't once stop the sun rising!