if he is flirting on social media, he doesn’t respect you. And if you don’t respect yourself, he certainly won’t have any respct for you. Trust me, try to block him on all fronts.. cut off contact, and just give yourself time to recover and think. Don’t ruminate on things (like looking through texts, photos)… accept the pain but know it will pass.
Try an app called Mend, which is good for anxiety. It has some useful tools.