I am not so sure about the “dopo” here.
It is a difference whether I am tired “from teaching” or “after teaching”.
What would be the Italian word to use, if I want to express the reason for being tired?
“Per”? Or do i have to say “per causa di”?
This is the closest translation, yes. Of course, this implies that the reason you are tired is because you taught, so it is not completely wrong to use “from”, depending on a context we don’t know.
I don’t find the sentence very natural, it is grammatical correct, but kind of ambiguous. Also, I think most people would drop the pronoun “Io”. Unless one wants to contrast their experience with someone else’s, “io” sounds superfluous.
Also the sentence could be interpreted two ways:
“I am (now) very tired, after having taught” or
I am (usually) very tired after teaching"
Although without further explanations, e.g. “dopo aver insegnato per quattro ore”, I would tend to go with the latter interpretation.
Edit:
It occurred to me that this could be a translation from Englist to Italian, and using “per aver insegnato” sound kind of unnatural.
Indeed that is the case, the original sentence is the English one:
Thanks for this @mike-lima. Incidentally I think the “Io” here is another English way of emphasising “Me, I am very tired…” as in “Me, I prefer rugby to football!” lol
Right, you can think of it that way. If you do not want to emphasize the subject, of if you are not contrasting with another situation, it is more natural to omit the pronoun.