Tips for gaining healthy weight?

Visceral Mercenary • May you find your worth in the waking world.

I've got a 5 month old and a 2 year old so it's kind of hard to find time to get to the doctor. I'm planning to eventually if I can't manage to do it by myself. My 5 month old won't take a bottle so taking him anywhere is a huge pain in the ass, so I'd rather avoid the doctor for as long as I can.

I'm 25, 4'11", and 83 pounds. I'm very underweight. I breastfeed, which I feel adds to my problem. I feel like I have tried everything and nothing is helping. I've been on protein shakes and protein bars for two months in addition to taking a multivitamin and eating normal meals. It is so demoralizing every time I step on the scale and either my weight remains constant, or worse- I lose more! I'm so frustrated.