Hey, Adam. Happy you posted this because I know where you are coming from. About 2 years ago I was 5'7" 135lbs. I tried in the past to try and work out and I always followed some crazy dieting plan with a crazy workout and I just never succeeded. Right now I weigh around 183lbs. Quite frankly, I never succeeded until I stopped thinking about it so much.
Nutrition: Eat whatever you want and just make sure you are getting enough protein (1g/lbs of BW is a rough goal). Don't be scared of fats or carbs, just eat. I really mean that. Hit 3k cals, get your protein and eat like crazy. This will be the biggest source for change for you. If you need ideas to prep meals for on the go, or late night snack, high calories anything, there is so much info on the net about it. Make an effort to eat though!
Workout: I'm sorry I don't know what you do right now, but something with lot of barbell work would be my recommendation. Starting Strength, anything like that. This helped me build muscle everywhere on my body.
Mindset: I had the same feeling that whenever I gained weight it was in my midsection. It's all in your head, it was in mine as well. If you are lifting more in the gym, and eating right, you will grow. Believe in it. Before you know it people will notice the changes.
I don't want to try to oversimplify things, but for me that is what worked for me. I did the above and put my mind elsewhere, because I know I tend to over think and change things.
Get after it man, believe in it and give yourself a year and you will pick up a ton of gains.