This is VERY common, as the HCG is starting to burn your fat for fuel, which means you need less fuel. You do still need to fill yourself to capacity with the highest fat foods you can find. A trick of the trade that our support staff uses is to buy 1-2 quarts of heavy cream (or heavy whipping cream) and drink it throughout the day. It is delicious mixed with coffee, some flavored stevia, or even chocolate syrup (blend with ice for a really yummy milkshake!). Drinking your fat makes it a lot easier to get enough fat in your system. 

Do focus on high fat foods if you are not hungry. The higher carbohydrate foods will fill you up a lot faster than a pound of bacon will. Make smart choices!