Calm down! Your Hubpages ad program earnings are still with you. You have stepped in a new month , so it will show the earnings of this month only. To check your earnings of the last month , Go to my account -->click the earning --> then in the "Choose Report Type and Date Range" select either last time to see the earnings of the last time or select "all time" to check your all time earnings. When you will earn 50 dollars Hubpages will send you the money via paypal.
So, don't worry about it.