Friend hasn’t texted me back?

So I get really anxious when it comes to friends and I tend to overthink a lot. I think it’s from when I was in middle school & high school, it was always hard for me to keep true friends. Anyways, I have a handful of friends I’m still close with from college. My friends and I hung out last week and agreed to go out to eat last week. I texted a friend and he didn’t respond till the next day saying he couldn’t that weekend, but this weekend. I texted him and another friend last night. One responded but the other didn’t. I texted him again today telling him what our other friend said, but nothing yet. I know he’s in school, working, and takes a while to respond sometimes but idk I just overthink a lot when it comes down to this and am not really sure what to do next. I guess I’m “worried” he won’t text me back, but idk why he wouldn’t? What do I do next?