how to wean an ebf baby because of pregnancy?

hello there iam now on my 6th week of pregnancy and i exclusively breast fed my 22 months old son. my OB advice me to stop breastfeeding because of a minimal hemorrhage. im on medication (duvadilan & duphaston). me and my husband. are having a difficult time to wean my son. we offer him a formula milk and my son always refused to drink. the OB also suggest to put something on my nips so he will refuse to latch, and earlier i put ketchup on my nips. he freaked out because he thought it was a blood. he still latch but he unlatch quickly when he tasted some ketchup. he cried the hell out. my mommy heart brokedown. but i did not offer him my breast and insist the fm but again he refused. ??? im so frustrated fellow mommies. please please help me. thank you in advance.