It takes time to get used to eating more and being able to take in such a large amount. I'd recommend getting some type of protein supplement.

Just make sure what you're getting is quality stuff, don't buy something because the sales rep tells you it will put on 50lbs+ in 6 months. Read reviews online and make your decision before buying. I'm a fan of Optimum Nutrition 100% Whey Gold Standard...it's probably the best bang for the buck quality wise. I love the stuff. 16ounces of milk plus one scoop of this stuff is 44grams of protein. Add in foods and other stuff and it makes getting in that 1gram for every pound you weigh a lot easier than trying to take that in with food alone. Grab yourself a shaker cup and just start chugging these things and eating healthy like a mad man.

Another recommendation is, if you do have trouble at first taking these things consistently and getting them in all the time. At a very least take one right after finishing a hard workout.