How to gain weight

Po
I gained 50 pounds during pregnancy and have lost a bit more than that. None of my clothes fit now and I'm worried about maintaining my milk supply for my 16 month old, who still wakes up to nurse at night. What are some healthy ways to gain a few pounds? I already eat super healthy so I don't want to just eat a lot of cheesecake or something. But I could. 
At this point I'm not worried about my weight per se, but I've been steadily losing since baby was born and I'd like to at least maintain my prebaby weight! Also my husband misses my butt.