I am heartbroken?

I am talking to this guy for a month now and he was in a 2-3 year relationship before me. And we follow each other on social media and he's got me as his wallpaper alongside with his deceased mother. Anyway, we like each other but I've been seeing him repost videos on his page that say "losing her was one thing but seeing her with someone else is another" and another was "deleting pictures of her but finding that one you took that was your favorite one"

I spent so much time with this idiot, and now I feel like I am the placeholder/rebound.

Am I overreacting? Any advice?
I am heartbroken?
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