For a thin 118 pds, 5'5 woman, when should i show in pregnancy? at 5 weeks, slight pouch but has always been there. current pants measurement is 27 in

Varies: It really varies across body types, people, and pregnancies. Some people show early, and some can be six or more months along before anyone notices. And women who didn't show until later in one pregnancy may look pregnant earlier in another pregnancy. Time to "showing" doesn't have any correlation to baby size or health of the pregnancy.