How did you get over your first love?

It’s been three years since we broke up, she was so mean and toxic nobody understood why I missed her. She showed me she cared sometimes and would act like she loved me sometimes and my brain just can’t let go of it. We have talked on and off since then, she would be nice at first then go back to being herself and every time I would get my hopes up. I just blocked her today for sending a picture of another girl after last night I just asked her how her exam went. I told her something like, if you’re talking to someone new I don’t want to get in the way of it and I don’t want to be too much or annoying, you could’ve just told me if you wanted me to leave you alone and I will. She responded it’s fine, then I blocked her. I know I am just hurting myself every time I talk to her, but I just can never fully understand or accept why. I know we were young but just how could she act like she loved me so much and make all these promises to me then leave and move on like I meant nothing. I just cling to her so much because I feel like I will never find love or someone who “cares” about me again. This time hurts more than the other times. Maybe because the other times I still had hope deep down or the thought that she’s changed, but I think I see now that shes the exact same. It still hurts so bad, I feel like I can’t live with how much it hurts but I have to, it’s just so unbearable. I also almost constantly check her reposts just to see how she feels about me, and it’s addicting and I don’t know why I keep doing it. I just miss her so much, I miss who I thought she was so much.