I put on 10lbs in just under 4 weeks using Rippetoes Starting Strength routine and eating...alot. Sure it wasn't all muscle, but some is and I'm hoping to add another 15-20lbs before cutting. Like you, I've always been very skinny. It's taken me about 15 years to realize what these guys have already said. EAT!!! And when you're full, eat some more. lol