Help to gain weight..

I'm in need of help to put weight on and keep it. I've had two children and currently pregnant with my third. Every time I give birth I go back to my pre pregnancy weight and I am happy my body bounces back I'm not complaining but I need a way to keep weight on or even gain weight in the first place. I hate the way my body looks I have bones sticking out everywhere and I feel like I don't look like a women I'm 25 years old and feel like I look like a young girl not a women. Any advice to help me gain and keep the weight on would be very appreciated. I also want to breast feed but I'm worried I will end up loosing more weight from breast feeding. I am only putting this in general pregnancy as I don't really know where else to place it. Xx