4 years out and 9 weeks pregnant!

I had my surgery a little over 4 years ago. We found out about a month ago that I'm pregnant!This is my first time, too although I'm 36! We are super excited. The only thing I'm worried about is gaining weight back. I already gained about 20 lbs bounce back. My doctor said it's reasonable to keep my weight gain at about 20 more. That will put right back at 200 which I'm terrified of! I know I have to eat healthy for my baby, but what can I do to minimize the weight gain? Exercise has been a little restricted because of a torn ham string. It's getting better finally so I hope to be able to start walking and yoga again soon. I do have to snack a lot, because if I get empty, I get sick!

Any suggestions would be helpful!

I'm 3 yrs post op, 40 and pregnant with #3!  My boys are 10 and 12 yrs old!  I'm almost 31 weeks and have put on around 35 lbs, I was normal BMI when I got pregnant.  I am not surprised with my weight gain-I have not exercised with the pregnancy and had been exercising 3-5 times a week up until about a month before I got pregnant.  I am just doing my best to listen to my body and keep the junk food out of the house and out of my mouth!