I'm 20 years old, i'm a twin by the way and i was born premature. is there any chance or way that i will gain weight.

Resistance training: I am going to assume that what you want is to gain lean muscle mass now that your adult height has been reached, and also that you are doing resistance training and discovering you are a "hard gainer". Ignore all advice about increasing calories, read a scientific book on nutrition, work hard in the gym, avoid steroids, consider creatine & an electric muscle stim unit if ok with your physician.