Breastfeedig weight gain

I've been an exclusive pumper for 5.5 months and I'm noticing over the past 3 months that I've been gaining weight. I am now 6 lbs over my pre pregnancy weight, which I went below the minute I got back from the hospital. I am always hungry and become very lightheaded and shaky every time I try to cut back and diet. Anyone else have a similar experience? Or any advice? I don't want to quit bf but I also don't want to keep gaining. Thanks