Weight gain/loss at 15 wks+2

Da
I am currently 15 wks + 2 days.  I haven't starting showing or gained any weight.  I lost 13 lbs during the first 10 weeks but I haven't gained any of that back yet.  This is our 4th baby and I lose weight during every pregnancy.  I'm concerned because I normally would have gained some back by this time.  Any one else experiencing this?