According to me it must be annu who is pregnant. After reading all the updates i felt that annu must be pregnant as she is shown to spent nights outside, even the astrologer says that there will some problems in her life intitally and then everything will be alright. The doctor says that Mrs.Walia is pregnant, it might not necessarily be Bani.
I feel theres no way that bani cna be pregnant as she's not shown having physical relations with anybody at all.