Breastfeeding = too much weight loss

My son is 6 months old and I exclusively breastfeed (no formula but we have now added baby food of course) so I have lost 48 pounds since I had him. I used to be a nice 148 but now I am 125 (I was 173 when I went to give birth) and I literally feel too skinny. I have always had a nice butt, but now I have nothing. I feel like I could blow away with the wind. Anyone know of easy ways to gain weight? I try to eat as often as I can but with a 6 month old and a full time working hubby, it's hard to find time. Please help!