Breastfeeding and being pregnant again

My daughter is almost 9 months old and we have just learned that we are expecting baby number two! Not exactly planned but hey I had a ton of fertility issues in the first place so I'll take this as a blessing and I am overjoyed. I just wanted to know if it was ok to continue to breast feed and be pregnant at the same time. Also, how many calories should I be consuming?  I'm 10 lbs lighter than before I got pregnant the first time. Any info is welcomed!