I'm 5'4, 49.5kg, 19 years old (female obviously)
I'm trying to reach 57kg/120 pounds but it was a struggle to even get to what I am currently.
Last summer I was 54kg/118 pounds and I want to go back to around that but I'm struggling to gain weight again. Ive increased my calorie intake and I make sure I'm eating plenty of protein etc.
I work out twice a week, before it was 3 times a week, not too much cardio & more weights.
You say you've increased your calorie count, but what to? I had a friend who insisted that she was eating "loads" and had increased it loads, but it was still only about 1100 cals a day which I think I have before about 10am ha ha (exaggeration, obviously).
You seem to be following the correct process.
But all I can think is that you are not eating enough calories. Many people believe they are eating a lot to gain weight, but in reality you are not.
Calculate your BMR, then do it from there.