4 months post breakup and feeling worse

Hi everyone, I just recently got dumped on my birthday after 6 long years together with my first love. We were highschool sweet hearts and this breakup was so sudden and unexpected. I’m truly having the hardest time, as soon as he dumped me he refollowed the girl he went to junior year prom with. She’s always been an issue, nothing ever happened but it was more so a self confidence and insecurity issue that stemmed from me bc he basically was almost dating her right before me. Anyways, he refollowed her right after he dumped me, and now he likes all her pictures again and everytime I see it, it shatters everything inside me. I blocked him and her from everything so I can’t see anything anymore, but I feel like i will never get over this pain. I feel such a deep hurt in my chest, i don’t think i will ever forgive him or move past this because unlike him, i truly loved him so damn much. I would have done anything for him, although I can’t say the same about him for me. There’s so many red flags looking back so i don’t know why i can’t get over it, i feel worse than i did before because i think reality is setting in that we’re done for good. Please tell me it gets better because I’m really losing hope right now. Everyone says it passes, but i don’t think this ever will. I don’t know how to keep going when I’m so depressed and hurt inside. He has completely turned into someone I don’t know, I’m not understanding and i can’t wrap my head around this. I keep having flashbacks of our memories, and thinking about him sleeping with someone else the way he used to with me sickens me. It puts me in such a depressed state, especially thinking about it being with that girl that i can’t stand.