Got broken up with out of nowhere and now I'm struggling

My ex broke up with me last Sunday. We had just spent the whole weekend together—everything seemed great. She told me she loved me, kissed me goodbye, and we even made plans for the next weekend. The next day, she didn’t respond to my texts all day. Late at night, she messaged saying she’d been asleep, then shortly after sent a long message basically saying, “I love you and you’re great, but I don’t feel the same anymore, so it’s best to break up.”

I tried to talk it through, told her I loved her, and, to my shame, begged her not to leave. I said we could fix things or I could change, but she replied that there was nothing more to say. Since then, I haven’t contacted her. She only reached out twice: once to return my stuff, and once to check if she left anything at my place.

I’ve been feeling devastated. I even went to the doctor because I couldn’t function. He prescribed antidepressants and recommended therapy—turns out I might have anxiety and depression.

What hurts even more is seeing her social media (I know, my mistake). She’s been posting stuff like “It never existed, I just idealized it” and “I was just a partner, not your love,” plus a novel quote where someone says they’d fight to keep the person they love. It makes me feel like I’m the one who dumped or hurt her, when I didn’t. I really loved her.

Why would someone post things like that after ending things themselves? Why twist the narrative and say I didn't love her when I did? I wouldn't feel like I do now if I didn't