I apologise in advance for the anecdote.
For a year I have been going to the gym 3 times a week and after recently weighing myself I have found I知 the same weight I am when I started. During the course of the year I have been lifting heavier and heavier weights, as the lower weights started to become too comfortable. I guess it痴 a given that since I知 the same weight I知 the same size as when I started, but I am more toned now.
On workout days I知 doing all the pre and post workout meals including protein shakes and on days I don稚 work out I don稚 take protein shakes.
Also I only use machine weights since I have hypermobile shoulders and have been told by doctors to use supported weights, so I never use free weights.
I知 6 foot and 138lbs so I知 pretty sure there is room for me to fill out.
Any ideas on what I知 doing wrong or what I should start doing to get bigger?
How old are you?
138 is pretty small. For people to help you better we would need to know, for example, what you started bench pressing to what you bench today?
If you want to get bigger, you need to seriously start packing on the calories. Why don't you take protein on non workout days? You constantly need to fuel those muscles, every single day. A typical diet would be like this (this is a massively broad example and not specific to you, guidance only):
Breakfast: 3 egg whites and 2 slices wholemeal toast
Snack: Protein Shake
Lunch: 100g meat & 100g carbs (weight not actually 100g of protein in your meal)
Post Workout: Protein Shake
Dinner: 100g meat & 100g carbs & few green veg
Snack: Beef Jerky/Nuts/Peanut Butter/etc.
Total Protein (dependant on shakes used): 200g approx
Total Carbs: 60-80g
Fats: 20g max (remember some fats are good)
For someone like you, you would probably need to fit another meal in there, seeing as you weigh on 138 pounds and you want to get bigger, but I'm concerned about your age.
I've been told that muscles can only take 20g of protein per hour, this can vary 5g dependant on the person approx. but the rest is turned into energy, and if energy isnt released can turn into fats. I wouldn't recommend anyone throwing down about 2 chicken breasts per meal as it's expensive or unnecessary.
I aim for 20-30g of protein every 2 hours or so, hitting around 200g a day.