Yeah... I was 128 when I got pregnant, and it went on fast. (Mostly because all I was doing was eating and sleeping.) I was 208 at my heaviest, and after the birth I lost nearly 50 pounds of that. (Babies, placentas, fluid, etc. and I also lost a lot of blood.)
I didn't have to gain that much weight, by far, but "When you're expecting Twins Triplets and More" highly suggests at LEAST 45 pounds for the entire pregnancy.
I gained over 40 pounds with my singleton and lost it all within 6-12 weeks (and I did not breastfeed long for a variety of reasons). So, no need to panic. My doc was worried about my weight gain as well... silly doctor.