Buddy, all the above aside you need to look at the weight you are pushing. 100lbs...you shouldn't expect much size. Plain and simple.
Not being mean at all just calling it like I see it. You can have a fairly crappy diet and still develop a descent body (albeit not shredded) and a pretty massive chest if you push good weights and exercise consistently. But, you have to work with fairly heavy weight.
I don't care if you weigh 145-180lbs you should be benching 225 at least
My tips: increase 5-10lbs a week for the foreseeable future... Eat healthy, lift progressively heavier, and you will see some growth. Keep a journal to make sure you do not stagnate and log all your lifting. Also, don't over train.