How can I improve my relationship with my long time crush?

I’m in eleventh grade. I’ve known this girl since first grade (let’s call her Elizabeth), but I had a crush on her since 8th grade. In 8th grade, I liked someone else (let’s call her Allison) and I started talking a lot with this girl. My crush on “Allison” ended in heartbreak and “Elizabeth was there for me since I started liking “Allison” and even tried to help me out. By the end of 8th grade, I had a crush on “Elizabeth”. When 9th grade started, I still had a crush on them, but didn’t have them in any classes, so we rarely talked. When tenth grade began, I realized that in 8th grade, they liked me, but I was too dumb to realize it. The signs were all there, and they even said that they loved me multiple times (after commenting them or supporting them on a matter). Then, in tenth grade, they were completely ignoring me, barely talking to me ever. This made me very sad. The worst part about it is when I tried to talk to them on Snapchat and they read my messages and didn’t respond almost every time. Towards the end of tenth grade, I was talking to them one night and it was the best feeling I’ve ever had, but then it went back to not talking once again. Now, going into eleventh grade next year, I rarely talk to them once again. I miss them and would do anything to be with them, or at least have our previous relationship back, and hate myself for not doing anything about the fact that they almost definitely liked me in 8th grade. What can I do about this?