madman
Super Moderator
More than likely your calories are too low. You say your taking in 3000 calories daily and you are naturally lean? Not sure how many of those calories are from complex carbs but to give you an idea I was always naturally lean and it was not until I went up to 4000 calories daily that I really started gaining but what made the difference was the amount of complex carbs (starch), I had to go up to 500 grams day which is 2000 calories from just carbs add in 200 grams protein (800 cal) and 135 grams fats (1215 cal).Try upping your complex carbs but also make sure you are taking in enough protein and healthy fats!