In addition to some carbs as greymouser suggests, consider adding fatty meat (or butter/coconut oil) more frequently. Why? Muscle cells (myocytes) are made mostly from FAT, not protein. (Hat tip Paul Jaminet). Without plenty of fat, you cannot build more muscle - of course, protein is also required.
Anyone who knows anything about gaining or getting bigger says you need to do three things:
1. Work out heavy/high intensity - sends the growth message to your body.
2. Rest/sleep/recover - this is when you actually grow.
3. Eat! You simply can't grow if you don't eat enough.
In the words of Mrs. Claus: "Eat, Santa eat!"
Or from My Big Fat Greek Wedding:
Maria Portokalos: Ian, are you hungry?
Ian Miller: Uh no, I already ate.
Maria Portokalos: Okay, I make you something.
Edit:
You seem to be afraid of saturated fat, which is only normal, considering the message that the media has been blaring for 40+ years. My counsel would be to educate yourself further into the truth of the matter. Some things for you to consider:
Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease http://www.ajcn.org/content/91/3/535.short "A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD."
Chris Masterjohn on cholesterol: http://www.cholesterol-and-health.com/
Dr. Eades review of Dr Malcom Kendrick's book "The Great Chlesterol Con" http://www.proteinpower.com/drmike/statins/646/
Anthony Colpo has a book by the same title
Gary Taubes "Good Calories, Bad Calories" pretty much destroys the diet-heart hypothesis (that eating saturated fat or cholesterol has any association with heart disease)
"Fat and Cholesterol are Good for You" by Uffe Ravskonov
And from Tom Naughton, some no-bologna facts: http://www.fathead-movie.com/index.php/no-bologna-facts/
