How do you know where you belong... Thats a hard question and the answer is different for everyone. In a nutshell, it just feels right. As you take the time to read and learn you find the path that feels right to you, that aligns with your beliefs and makes the most sense for your life.
Many Pagans came from Christian backgrounds at one point but I honestly don't think it matters what you came "from" because no matter what it is a difficult think to let go of old beliefs to make room for new ones.
Catholicism has its place and works for many many people. Thats great I think. To each his own. I harbor no ill feelings about my Catholic upbringing. I feel that there is something to learn from every religion, even if what you learn is that it isnt right for you.
So a few books that might help you find out what Wicca is and if it is right for you ... Here are a couple that would be a good start.
Wicca for the Solitary Practitioner When Someone You Love is Wiccan I also recommend you read my article on
The Charge of the Goddess and see how you feel after that.
Best of luck to you