Try keeping a food log.After two weeks of writing down everything you eat,add it up and see how much you're eating.Then,if you're not gaining any weight,add in 500 calories from there and keep adding in 500 each week until you reach your goal.If it's that bad,try eating some pizza and wash it down with some whole milk every week or on the weekends.Make sure you're eating plenty of carbs too.Pasta might be your best friend when bulking.Your current weight seems to be your set-point.Here is a list of some quality foods that you can add into your diet to make eating like a pig easier:
2 tblspoons of peanut butter(I like crunchy):210 calories,9 g protein,16 g fat,6 carbs.
1 tblspoon of olive oil:120 calories,14 g fat.
One cup of whole milk: 120 calories,8 g fat,9 g protein.
One slice of pizza from pizza hut:about 350-450 calories.
A homemade double cheeseburger(with lean beef): 695 calories,25 g fat,88 g protein.
One can of AMY's chili:380 calories,12 g fat,16 g protein,40 carbs.
You see,there are many ways to add in extra calories. At the end of the day,just add in 2 tblspoons of nut butter.That would be an extra 420 calories. If you're doing a lot of cardio or play a lot of sports,you're gonna have to eat more calories too.Like maveric said,drink a bunch of whole milk or 2 % milk.