yo me quejaba
I used to complain / I was complaining
tú te quejabas
you used to complain / you were complaining
él se quejaba
he used to complain / he was complaining
nosotros nos quejábamos
we used to complain / we were complaining
vosotros os quejabais
you used to complain / you were complaining
ellos se quejaban
they used to complain / they were complaining