Can I gain 20 lbs and still have a flat tummy?

hi..I am 44..had a baby at 41..always worked out..I am lean and have a lot of muscle . I work out with 5 days a week..My question is if I gained 10 lbs..and added some fat on my body, could I still have a flat tummy..and would this fat giggle? I am 5ft3in..105 right now.
I meant 20lbs..or should I go just 10..or none at all..I just think I need some fat on my body ..to add more of a womanly figure.