what is wrong with me

so im dating this guy max (24) for 3 months now. but we knew each other before, 3 years ago. we dated for a month back then but he ended things with me for his cheater ex. he has told me its because he thought he wasnt good enough for me, he wasnt healed enough for me back then so let me go. but now I absolutely love this guy i adore him, he is loml actually. but those memories still linger, the fact he was with his ex recently before me (the samw one he left mw gor 3 years ago) he stalks her socials. and im so jealous of the memories he has with her, thw places he has been with her. to talks to me similarly like he would talk to her. I get that it is 4 years of a relationship but im extremely jealous of what they had. idk what to do, how to get over it?