24, and started lifting again March/April trying to get to 210-215lbs (currently between 175-190 [fluxuates crazy] and can't stay above that) muscle mass. I eat plenty of steak, chicken, rice, eggs, grains have supplements etc and lift "heavy" (for me) weight but cannot seem to build. I also push myself and up my weight bi-weekly
Everyone metabolism is a bit different. I have to eat 6000 cals a day to gain weight. Up your calorie intake and up your protein intake. You need to keep track or else you might end up fooling yourself. There is a good plan on bodybuilding.com called shortcut to size. I recommend you go and read about it.