Multivitamins for breastfed babies

Hi! My 2 months old baby is currently on full breast milk. The doctor prescribed Enfamil multivitamin supplement for the baby. After taking it, we noticed that baby poops lesser. He usually poops a few times a day but now he only poops once every 2 days. The smell of the supplement is also very strong and baby doesn’t like it. Is it necessary for breastfed babies to take multivitamins ? If yes, Which brand is you baby taking?