Ectomorphs have an extremely hard time gaining muscle weight. It really sucks for us. I havent gained much muscle mass but I have gained more definition and strength with eating 1.5g of protein per 1# of body weight, the more protein you can eat the better! Lifting should be short and intense!!! (I was doing a workout based on Body by Science, it works)
I would also check in if you have any food allergies or intolerances. (grains, dairy would be the first two I check into)