For some nursing moms it's perfectly normal to carry 5-10lbs above pre pregnancy weight while they are nursing. Guess it's the body's way of making sure there is enough for you, baby and to replenish the stores lost during pregnancy. Your body is making up for a lot of losses and maintenance. And you are making sure a whole human is growing!
I had the same thing happen while nursing my first. Couldn't figure out for the life of me why those 10 lbs were hanging on. Of course I read it's perfectly normal *after* I weaned at 16 months and then dropped the weight! lol
And if you are hungry all the time you need to look at what you are eating, how often you are eating and making sure you are drinking lots and lots of water. Sometimes when you feel hungry it's actually thirst! Try eating 6 small "meals" per day. That way your body never does without for too long. Great snacks are things like peanut butter, apple and skim milk, cottage cheese and fruit, edamame, a handful of almonds, whole wheat english muffin with a little peanut butter, yogurt with some fruit and granola, etc.
Don't skip breakfast either. Your body will be trying to play catch up all day.