Gosh Jordan I think it be a combination of any of the things you listed.
Since you were away, give him a week or so to see if he gets back into normal routine.
My pets all sort of behave strangely when I've been away & it'll take a few days for them to get back into normal routine around here.
If he continues to behave strangely after a week or so, then I'd start to be concerned.
-----
PHRatz