@hecks, sup! I'm 21, a former Southern Baptist and, as much as I understand of secular humanism, identify with it. I know exactly where you're coming from, although I personally converted away because of an evaluation of what evidence I had for the hypothesis. I am however familiar with such feelings of guilt and am glad you appear to have found something that fits.
@YJ: More or less, yes, the agnostic modifier does cover this. It's helpful to imagine two axes -- "knowing"/agnostic, for left/right and theist/atheist, for up/down. ("Knowing" can simply mean "not-agnostic" here, I just don't know a good antonym to agnostic, because "gnostic" is something else altogether.) The vast majority of atheists lie in the lower-right quadrant, though there are a few in the lower-left quadrant. I'm actually not certain where to classify most theists and would not want to speak for them, but there are certainly plenty theists who fall into either upper quadrant.
I think it is more helpful to see the question as having two dimensions rather than one; certainly a statement of one's knowledge and a statement of one's belief are separate things, and merit their own modifiers.