Unless you're a notorious hard gainer, you should have been EASILY able to put a good 40lbs on just from diet alone!!!
I'm going to say without a shadow of a doubt now, that your diet is 100% the issue. Even with your weight at 140lbs, 155lbs; you're flat out wasting gear. There's no kind way to say it or sugar coat it.
You're diet is what needs serious attention, not questioning your gear. I'm pretty sure everyone who's posted in this thread thus far is going to be in agreement with me as well.