In Portuguese there are several ways to refer to something that happened in the past, each with varying shades of meaning. The present perfect tense includes expressions like these:
Use it when talking about action that has been happening (and still is).
This is one of the most difficult tenses to get the hang of for several reasons. Everyone gets hung up on the fact that in Portuguese you don't (generally) use the verb to be to express been as we do in english. If you did it would be estado - and you actually can (and should) use it like this:
This is fine, just a little formal sounding. Brazilians would say something more like, "Eu ando muito cansado esses dias".
The second reason this tense trips people up is that it's unlike other conjugations in that the form is TER + PAST PARTICIPLE.
ter (in the present) + past participle
|I have been working||eu||tenho||trabalhado|
|he has been woring||ele||tem||trabalhado|
|we have been working||nós||temos||trabalhado|
|they have been working||eles||têm||trabalhado|
-er and -ir verbs
|I have been watching||eu||tenho||assistido|
|he has been watching||ele||tem||assistido|
|we have been watching||nós||temos||assistido|
|they have been watching||eles||têm||assistido|