What does it mean if someone breaks up with you and promptly gets on dating apps?

My boyfriend and I have been together for 5 years. Sunday at 9pm, he broke up with me, saying that he's struggling with trauma and other things and just wants to be alone while he deals with it.
Within 12 hours he got a tinder account (we were sharing an email and I hadn't taken myself off yet, so I saw the sign up email). I just saw his Instagram account where he posted a pic of his Snapchat saying, "if you want to chill and talk, hit me up."
He's been acting rude when I come over to get my stuff, but he also keeps hugging me and giving me kisses on the head. I know it's stupid to be friends with your ex, but it's still so fresh and I still have things to get, so I'm still just confused.
I'm a wreck. I'm having heart palpations and can't sleep. Meanwhile, he's doing this. I feel like I never mattered to him, like i wasn't good enough and like he just left me so he could hook up with people. I don't know what to think, I just know I'm in a lot of pain and really confused.
What does it mean if someone breaks up with you and promptly gets on dating apps?
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