Generally you will see the full form of a stressed pronoun, but some object pronouns will form a when used after the word com(with). For example:
Você quer ir ao cinema comigo?
Do you want to go to the cinema with me?
However, this does not take place if nós(us) and vós(you, pl.) are followed by outros(other), mesmos(selves), todos(all), ambos(both).
Terá que fazer o trabalho com nós mesmos.
You will (really) have to do the work with us (ourselves).