Eat more. Like your weights, train in a progressive fashion eating a little more and then a little more everyday. Liquids are a good way to get calories even when you feel full. Eat your 3-4 normal meals a day now add +pint of skim milk a day. When you platuea change to 2% then whole. Then go to to a half gallon then a gallon. Before steroids came in the late 1950's people wanting to grown would drink a gallon of whole milk a day while following a program of hard & heavy squats. It performed miracles.
Squats, Deadlifts, Bench, wt, dips, leg presses--the big compounds done for 4-8 reps cause the body to release testerone and make you grow larger in addition to localized muscle stimulation.
Google 20-rep Breathing Squats and 5x5 programs. Avoid isolation movements avoid working for a burn or a pump or a feel or a shape--work to put a little bit of weight on the bar every workout.
Add more sleep. Move to 9-10 hours a night.
Gains of 15-30 lbs in a month have happened by simply adding sleep and an extra gallon of whole milk a day while doing 2-3 hard workouts a week. 80-100lbs in a year is not crazy in an untrained lifter or a volume "pumper" who suddenly trains correctly.
Depending on your metabolism you will gain some fat. Your body set point won't change unless you do. This is why its called bulking.
I gained 15 pounds in a month and 30 total over 14 months after I did this and gave up that Weider stuff.
You can do it! (firstname.lastname@example.org)