My mom knows I'm an atheist! And it's okay! I had been scared to tell my parents, but my mom was really calm about it and told me not to worry about what other people think and that she accepts me no matter what! Turns out that my brother is an atheist too, I had my suspicions and now I know for sure. I'm still not telling my dad as he's pretty active in the church (and he helps me pay for college, still have to wait until I'm financially independent for that conversation).
I feel like some of the weight is off my shoulders now. Future conversations with relatives are looming, but for now I'm relieved and happy!