Hi waternymphh!
Have you ever been tested for food allergies? If you have a history of things like anemia or IBS you might want to look into that, allergies to things like wheat can cause malnutrition in an otherwise healthy person because it inflames the digestive tract to the point it can't absorb nutrients.
My sister has the same problem you do, she is maybe 100 lbs at best most days...with stress, even smaller. She eats plenty of food, she just can't gain weight easily. She's a vegetarian, but had to start basically eating like a body builder and doing weight exercises to put on muscle because even though she is thin, she feels out of shape! Some people forget thin doesn't automatically mean in shape and healthy!
She eats lean proteins, healthy fats (nuts), plenty of fruit (especially berries), whole grains (brown rice), and lower carb veggies (like asparagus, broccoli, greens, etc...) She also drinks protein shakes and tries to eat frequent meals and snacks. Oh, and she had to quit the caffeine habit...no more coffee. The only caffeine she gets now is from dark chocolate.
Zeebs is right about muscle building, odds are it'll be the best route to getting the body you want! I'm reading a book right now you might want to check out, it's called "The New ME Diet" by Jade Teta and Keoni Teta. They are naturopaths and personal trainers with a background in biochemistry. Their book talks about how different bodies burn different things for energy, and your body type (and my sister's) fits into one of their 3 profiles. In the book they outline food and workout suggestions to help put on muscle and balance the body's hormones to keep an even weight. I'm not done with the book yet, but I really like how their approach is not "fad diet" like, but more from the place of how people should eat what fits their body best, what it can use best, and focus more on 30 minute muscle building workouts 3 times a week and daily walks instead of hours and hours of cardio. Can't say that I agree with every little thing they say (can't say that about anything I read!
) but it has lots of good info in it...let me know if you give it a read!
Im 1.63 cm and just 45 kgs... I need to gain weight because I want to feel like a woman immediately 
you know it seems like I havent got breasts or hips because they are too small 
I am looking like a small girl in her early teens( actually 22) oh my gosh! have tried lots of things Im tired though... I ve been trying to gain weight for so long.. Ive done lots of things, went dietician,ate,ate,ate and ate but I ve never been able to gain a gr , sometimes I just did a tiny belly and thats all , thats really frustrating and pisses me off 
eating much doesnt work for me... so except from this...any recommendations for me?
thanks again hun 
