I just need some advice or kind words!

I am 19 and just moved into my very first apartment! After all the heavy lifting, I brought my cat into the apartment, and I've kept him in my room. I just did this today, but I'm super nervous about him developing kitty depression since back at home he had two kitty friends, and now he has none.

I'm very worried about how this will affect him, especially since the room is much smaller than my room back home was, and there are still boxes and such that I need to unpack.

Could he develop separation anxiety? I put him in my room, gave him some treats and stayed with him for about an hour, but then I had to run an errand, and it ended up taking about an hour and a half, and when I came home and went to my room, he was exceptionally clingy and sweet (more so than usual, lol!).

Sorry this is so long; I'm just a worrywart and want my cat to be happy.