Rule for changing voice of past continuous tense – 

Active VoicePassive Voice
Subject + was/were + verb[ing] + object Object + Was/were + being +verb [past participle] +by/with/to + object 

Examples

Active VoicePassive Voice
She was washing the dishes.The dishes were being washed by her.
Nandita was watching a romantic movie.A romantic movie was being watched by Nandita.
They were eating breakfast.Breakfast was being eaten by them.
The bird was feeding the chicks.The chicks were being fed by the birds.
The cow was eating grass.Grass was being eaten by the cow.
Mother was making a sweater for me.A sweater for me was being made by mother.
The teacher was teaching us a lesson.A lesson was taught to us by the teacher.
The government was making useless schemes.Useless schemes were being made by the government.
We were writing essays.Essays were being written by us.
He was asking me several questions.Several questions were being asked to me by him.