Protein powders have been mentioned, try keeping your protein sources mainly whole, eggs, beef extra, is a good idea.
Simply from the extra amount of calories and food though it puts strain on the digestive system. Most people are deficient in hydrochloric acid as it is, with the extra food it only makes the problem worse.
I would highly recommend getting some hydrochloric acid with pepsin if you are trying to gain muscle.
You can do this test to workout exactly how much you need:
http://www.charlespoliquin.com/Supplements/acid-test.php
But even getting some and adding it in and making changes over time will work.
You could also have food allergies, although that probably isn't the problem if the symptoms only started after you increased how much food you eat.