i'm feeling DOWN. my ex moved on with his ex & i want to stop caring

hey all, i need some real words of encouragement so im coming here :). backstory, my (22F) ex (22M) & i dated for 2 years and broke up 6 months ago, did the usual on and off, hooking up thing for awhile and then sat down 3 months ago to say this is done for good.

a week later he started hitting up his ex girlfriend from 5 years ago (they dated for 4 months and she cheated) who ALSO just got out of a long term relationship (5 years). anyway, in the time that's passed they've gotten increasingly more serious i suppose? my ex & i have mutual friends, and he's been asking to bring her to parties and stuff - to which my friends have been saying no.

i can't speak to the validity of this relationship, i just have no idea why he's done this or what he's getting out of it. we had a very serious relationship and was both of our first REAL partnerships. now i can't shake the feeling of 'losing'. i just feel like a loser. everyone knows about this new relationship of his and it's just embarrassing. i'm over him, i don't want him back at all... i just want to feel like i haven't completely lost. like i'm not always the one hurt and left behind. it's exhausting. he broke up with me, he's cheated on me before, he was AWFUL during the breakup he used me A LOT, and now he gets to move on.

i don't even want a relationship i like being single it's freeing but i cannot stop comparing my experience to his and i can't stop feeling this innate sense of injustice. i've been so silent & so calm - i haven't crashed out once. it's not fair.

ranting and rambling but anyone who's experienced this... hmu :)🤙