too much weight gain

Help! I am 12.5 weeks pregnant with baby 2 and I have already gained 10 pounds! I gained 65 with my daughter and never lost it all, so I started out this pregnancy very overweight. I CANNOT pack on another 65 pounds. I had terrible nausea during my first trimester, so I pretty much ate all carbs all the time. I feel better now, so I need to get ahold of this weight gain. Any advice from other moms who have kept pregnancy weight gain to a minimum? I really shouldn't gain more than 20 pounds total this pregnancy and I am already half way there at 12 weeks 😱 feeling so stressed out!