saw my ex with a new girl and its making me feel like a fool even after 3 months of NC

i saw my ex hanging out with a new girl in roblox now, they both were nice to each other and although its been 3 months, I feel so fucking sick like my heart just dropped, idek if they are dating yet I'm out here feeling like a clown (I deserve it) maybe if I just fucking forget about him but why is it so hard for me even after knowing how he cheated on me and disrespected me so much, I feel so disgusted with myself at the end before blocking me, he told me I'm not pretty enough and it made my heart fucking burst even though after break up I started getting many compliments about my appearance which made me think my ex was lying but now its the complete opposite after seeing both of them, I'm acting up like a fool, I could msg a mutual and ask if they are a thing but Im again gonna be labeled as the obsessed ex, I'm actually gonna fucking cry why did he do this to me, he never loved me so how can he love someone else right away after me, I sacrificed my hobbies to spend time with him I'm actually tearing out here, I didn't know what to do anymore and I will see him at school tmr too that's even worse. I'm feeling like this even after 3 months of NC how pathetic