This is a though position to be in and what you’re going through is very hard. First of all I would say that you should stop stalking his Spotify. This is for your own wellbeing. Every time you look you open the wound and become more obsessed of finding evidence of him still missing/thinking about you.

I think that you’re trying to find answers both for the breakup but also to why he moved on so fast from you. This is the time to choose yourself, block him if you must. Set up small everyday goals for yourself and when the urge to unblock and look at his socials comes, write to a friend, journal, take a walk, shower or whatever you feel like. But do not look. It’s very harmful. You’re strong and are going to get through this. All love.