Staying a healthy weight during pregnancy

I’m so worried that I’m going to gain too much weight during pregnancy. I had lap band surgery back in 2005 and lost about 80 pounds, and was still ideally about 20 pounds from my idea of what my weight should have been. The moment I became pregnant, it felt like I bloated right up, and now I have put on about 10 pounds, and I’m only 3 months pregnant currently. Yikes! I haven’t changed my diet at all, but I’m wondering if its because I’m a bit older. I am 36 years old. I have an 18 year old, a 12 year old, and an 11 year old. Here we go again!