Am i stupid for caring

I just keep thinking about my ex, we split like 2 and a half months ago but I think about him every day. It's gotten less since I started working full time but even then he pops into my mind. It's like my stupid fucking heart yearns for him and it won't stop. Why won't it stop. I'm fed up of crying over him and missing him. We were together not even 3 months and he had this effect on me it's not fair. He was my first boyfriend. He got over his ex of 3 years apparently in 2/3 months so it probably took him to the evening of our break up to get over me😂 it's not fair because although it ended on friendly terms, he didn't put up a fight, towards the end he didn't even seem bothered about me. So why can't I forget him. It's not fair so many things remind me of him😓