Great information there from NiallX.
If it turns out you do need to eat more protein, stay away from protein powder (they use milk from sick cows because they can't sell it as fresh milk)
Cheese does contain a lot of protein but it's also very high in fat.
Milk is good as it has the same amount of protein regardless of which one you get (full, semi or skimmed)
But the yeardstick against which every other type of protein is measured is egg white. Egg white is the purest form of digestable protein available in nature.