my baby is 5mths too and on formula fed .. she pooped every 2days now .. i will always make sure she poop on e 2nd day, if still doesnt poop, i will give her gripe water mixed w fm or bm to help her tummy .. maybe you can try .. as long as its mustard yellow (peanut butter texture) and not watery, you shouldnt worry, mummy .. i used to worry but after seeking advice from doctor, its all good now .. :) hope this help clear ur worry
Ummkha