It's religion, Jim - but not as we know it. I certainly don't fit neatly into either the theist or atheist categories. My worldview is best described as closer to Pantheistic that anything else. That's the doctrine that the universe conceived of as a whole is god and, conversely, that there is no god but the combined substance, forces, and laws that are manifested in the existing universe.
In simpler terms, my view on Pantheism is that nature is the creator, provider and controller of all that exists. Individual Pantheistic worldviews vary but all have that one common thread of nature being boss. We do not believe in a distinct personal or anthropomorphic god.
Pantheism is not an organised institution. There are no common places of worship, no leaders, no scriptures, no commandments, no website with a 'donate' button. It's a very personal thing.
I was introduced to the concept while studying the work of 17th century Dutch philosopher Baruch Spinoza and have not looked back since. And I'm in good company - notable Pantheists include: