Once baptized Catholic, you are still considered Catholic by the Church even if you are non-practicing. There are three conditions one must meet for the Church to no longer consider you Catholic: 1. Decide to leave,  2. Demonstrate that you have left the Church, 3. Notify the Catholic Hierarchy (Please see the link below). If all three are met, you are no longer Catholic. Otherwise, you are still Catholic according to the Church, and in that case, you can return to the Church. It is suggested that you talk to your parish priest, who will most likely tell you to go to confession. It’s that simple!

For further information, please go to: http://www.catholic365.com/article/3808/if-i-was-baptized-a-catholic-am-i-still-catholic.html