16 weeks and weight gain

I had a dr appointment today. I'm 16 weeks and have already gained 11 pounds. The dr told me not to gain anymore. I'm kind of stressed out! My weight has always been an issue for me. My husband says he'll start exercising with me but I'm so fat now that it's hard to breath and my knee and groin and back hurt. Not to mention we both work full time (him usually around 60+ hours a week) plus we already have a 6 year old and we are just tired! Ugh. I'm just a mess... We'll see how this goes.