If I message a guy i like this on fb will it be super weird? What should I do? ILL ANSWER YOURS RIGHT AWAY?

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Ok so im 17 yo girl, very shy around people i dont know, socially awkward sometimes.I have zero experience with guys. There is this one guy who I find cute for almost two years now, even though I dont know him and he doesnt know me. Hes graduating in 4 days, and ill prolly never see him again. I dont have any classes with him, i do RARELY see him in hallways.
In December i msged him on fb saying hey. it never showed that the msg was seen by him, i think it went to his other inbox cos at that time we were not friends on fb and we had no mutal friends. Anyways i wanna do sth before its too late, i dont know if he has a gf :/ Will it be weird if i msg him on fb now? ( on Saturday he accepted my friend request ) I dont want him to think im a creep and stalker if he sees the msg from December. Would this be weird:
Hey! I know that we don't know each other too well, but anyways we go to same school, and I feel kinda stupid doing this, but I think your cute and since you're leaving anyway I just wanted to say that

I really do feel stupid doing this but I don't wanna spend the rest of my life regretting not doing a **** about it. PLEASE HELP ME