Baby hasn’t pooped in 6 days now

My baby was fed breastmilk and i started supplementing with similac pro advanced. i mixed formula 2 oz (pre mixed) with 2oz of breast milk and had to give a full 4 oz of formula. my baby last pooped on wednesday it is going to be tuesday. i contacted my pediatrician they recommend giving a glycerine suppository only half. MIND YOU HES 2 MONTHS old! we have tried warm baths more breast milk belly massages bicycles everything. he only is fussy till he passes gas then he’s fine? and i really don’t feel comfortable giving him medication for 2-5 year olds