You need not visit a doctor... At 7 days the baby is having only milk which is either absorbed by the body or passed through urine. Massage baby's stomach and do the cycling movement with the legs putting some pressure on the stomach while doing so.. atleast baby will pass some gas which could otherwise make them quite uncomfortable

not to worry dear,it's normal if baby's don't poop even for five days .if peeing no problem.just ensure u burp ur baby after each feed to reduce farting and bloating of tummy due to gas.take care