Let's clarify this. Have you been lifting 3 or 4 days a week for the last 5 or 6 weeks with no interruptions or missed sessions? What have those workouts looked like?
Like JFG said, all the advice we've been giving you for the last 2 and a half years still applies. Any program you were ever recommended and any simple nutrition tip you got is still 100% valid.
Since September 2013, you've gained less than 10 pounds. That's, like, almost intentional. If you've changed your outlook on training, that's awesome. But it still comes down to: Follow a basic, well-designed program for several months without interruption and eat 3 big meals every day of the week.
Young underweight guys almost have an advantage over other folks because their body is so ready to grow if it's told to (by training) and allowed to (by eating).
You don't need to "clean bulk" You need food. Plenty and plenty of food. A cheeseburger and an order of fries will not kill you.
For the record, I never thought you were a young piece of shit. I thought you were a young, easily distracted dude with training A.D.D. who always seemed to change focus. Pretty common behavior among that crowd. No worries.
But if you do start falling back into the same habits this time... :rageguy: