You sent 0.1 btc on December 11th with a 0.00033571 btc fee, it confirmed within 1 minute. Today, you send another 0.1 btc from the same address. This time, it really has 0 fee. It should confirm in a few days. Don't worry too much. If you are not sure what you are doing, do not send transactions with zero fee. It's going to cause you problems. Which wallet are you using? Do you know how to attach a fee?