J.D.
Yes you do need the extra calories. Your body is a work horse apparently. You are quite amazing to be able to do that much. I mean WOW!
So, you normally weigh about 135 which is normal to small for your height. If you were going to just maintain that weight without breastfeeding and being pregnant, you would want to multiply that number by 10... So your caloric base would be 1350. In the last 2 trimesters of your pregnancy, you should be taking in around 300 calories more than your base for your pregnancy. Also, they normally recommend 300 - 500 calories daily for someone who is exclusively breastfeeding. Since you are breast feeding 2, pick your range.
Personally, I would say to drink one more glass of whole milk with a graham cracker or two, or a bowl of cereal before bedtime. that should give you around 200 to 300 calories.
Good article: http://www.kellymom.com/nutrition/mom/mom-calories-fluids...
Congrats on the pregnancy!