Very emotional and sad girl problem help!?

Im starting to go into this loop and its not good. So basically ive had the biggest crush on this girl since 7th grade (im in 12th now) She is a family friend and i see her like 3 times a year woth other family friends and i dont think she likes me at all so by me expressing myself can make things very awkward and im scared. This has gotton so bad evreytime i see her the next 3 days to a week are hell and im only thinking about her and i get so upset that i cant have her. I think about her 24/7 for 5 years and she has no clue i like her because i know she doesent feel the same. She sees me as a bad person and im so sad rn i just dont know what to do to stop falling for her and it gets evem harder each time i see her.