I was …ing
I was painting.
I was cleaning.
J'étais en train de travailler quand c'est arrivé.
I was working when it happened.
Je pensais que j'étais en train de devenir fou.
I thought I was going crazy.
J'étais en train de jouer quand j'ai senti un tremblement de terre.
I was playing when I felt an earthquake.
I was bluffing.
J'étais en train de réfléchir.
I was thinking.
J'étais en train de t'appeler.
I was just calling you.
J'étais en train de le caresser quand il m'a mordu.
I was petting him when he bit me.