i need some one on one girl talk

so months have passed since the guy I loved moved without telling me 😭 I messed up by not telling him how I felt and now I have to suffer the consequences of not telling him. would he have stayed if I told him? I knew him for 3 years and I miss him dearly. I dated his friend and I knew it was wrong because I was still in love with the guy. I still am and idk if I would consider him my first love. I'm 13 and need advice. has this happen to you? if so how did you get over it because the guy moved around September-October.