I Feel a Lil Awkward...

So, I feel a bit awkward posting in here because most people are losing weight, but I wanna know a healthy way to gain weight. I'm a size 0 (95lbs) in America and i was a size 3 (110lbs) last winter and i lost all that weight in like a month. Along with wanting to gain that weight back in a healthy way, I want a way for my boobs and butt to grow a bit more. I loved my body back when i was 110 lbs. I want it back, but healthy. My boyfriend loves how I am either way and he loves the small amount of squish I've got. Thats part of the reason I want the weight back (I never meant to lose it in the first place, I just went through a really hard spot in life). I want to gain some more squish, butt, and boobs, but i want it to be healthy. Any tips? Im 17 years old and 4'11" if that helps.