Why is the guy I like patching me? did I say something wrong?

So... it's a weird situation. There's this guy I kinda liked for a couple of years now, there has always been a slight banter and flirting between us over the years (and I can tell you the chemistry Is definitely there) but we wouldn't see each other often at uni because we are on different courses.
He's into fitness (like me) and he would usually reply to my stories at the gym or while working out (he even offered himself to be my gym partner if I wanted one), one day he even said that my biceps were bigger than his (as a joke I suppose) so I challenged him for a wrestling match.
A couple of years ago I also heard from a couple of friends that he has told them that he thought I was v attractive to him, but I didn't do anything back then bc he had a girlfriend. We've been messaging on Instagram for quite a while, not very often, but when we would he would always be very nice to me and asking me questions showing that somehow he was interested in bits of my life. He would also send lots of "xx" but maybe that's just the way he texts. we even matched on Tinder lmao

A couple of days ago, my female friends convinced me to text him a short friendly message to ask him if he wanted to catch up ( as I just got back in town after the long lockdown break)... I know that maybe he was busy... but he has literally been online a lot and hasn't opened the message for almost two days, and I don't think he will anytime soon.
He never patched me like this before, he would usually either reply right away or would way a few hours, or the latest the day after if I texted him quite late.
Does he think I asked him out on a date? cause that wasn't actually my intention, I wanted to spend some time with him and talk like friends because we have seen each other only once this uni year, that's all.. why is he acting like I'm being clingy?
I know it might have been an out of the blue question but I thought he wouldn't have this reaction, especially considered the past.

What is going on?
Why is the guy I like patching me? did I say something wrong?
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