Egg whites are a normal and perfectly inexpensive food and you can get slightly over 3 grams of protein for one large egg white

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You can peform this excercise, might not be as effective as on a bench but its better than nothing
Barbell Floor Press
You also might want to try a modified flye. Lay down, use the dumbell bars, one in each hand. (Something like that picture)
http://upload.wikimedia.org/wikipedi...mbbellFlye.JPG
One of the important things about building your chest is feeling the contraction in your pecs. At the top of each excercise try to get a good contraction with your pecs.