Hi Adam, greetings from the other side of the world.
Like many others here I know exactly those feelings you describe. When I was leaving I used to wake up in the middle of the night scared, I used to look at myself in the mirror and not recognise who I was.
I spent about 5 years not even thinking about religion, then some time reading about many different belief systems. I did not find boards like this until around 5 years after I left and even then felt a little guilty, like opening pandora's box.
You may find that there is a lot of positive stuff you can take away with you from a Christian upbringing, I found it best to reflect on the positive. You now have total freedom to decide how you wish apply these values in todays world.
I only recently read Ray's book and even after 10 years it hit me that this was just another religion. I would reccomend it, it will help put everything into perspective.
Relating to other people may be difficult at first, for a while I felt like a foreigner in my own country. People in the world are not all bad, you will find people who share your interests and outlook, they will all have their own imperfections, however you may find an honesty in being able to relate to the imperfections in others and yourself without judement based on the old set of rules.
From now on you are a valuable and normal person in your own right with the same freedom of thought that we all now enjoy. Enjoy life, explore new ideas and people. In time you will build your own set of values based on your experiences. These are exciting times.
I wish you luck.
Alan.