Has anyone not gain any weight by their 3rd month ?

Aida

So I’m 5’5 , and my last weight before being pregnant was 163lbs. I’m not 3 months pregnant (16 weeks pregnant ) and my weight is 157. I’m still not showing but all my ultrasounds have been normal . Has anyone experienced this , when should I worry ?

This is my second pregnancy , 1st was a MC at 6 weeks .