Sorry for the lateness of my reply, but I just saw this and wanted to add my thoughts.
Mother's are worriers. They care very much about their children and worry about everything. I know I often have a hard time confiding things to my mother that I think would cause her to worry unnecessarily, and I especially had a hard time with this when I was first going to college. I think when we break away from home and start experiencing our own problems, we want desperately to figure things out on our own- without help from the parents- and we don't want our parents to fret over what we are trying to decide for ourselves.
The fact that you don't want your mom to worry shows how much you care about her. Just remember that you can't keep her from worrying. Your relationship with her will be stronger if you can share your struggles and enforce a boundary- let her offer advice if she wishes but make sure she knows that you are handling things on your own and don't want her to rush to your rescue. You'll let her know if you need her help.
As for how your feeling about your faith/religion- It sounds like you are going through what Fowler called Stage Four
of faith development. It is a time of doubt and struggle and self-discovery. You are thinking for yourself and becoming more critical about your belief and what you will ascribe yourself to. This is the time when you will be striving to identify your "core"- what is truly in your heart and soul, what you truly believe. When you've identified what has the strongest pull on your life and you commit yourself to it, you will have moved on to Stage Five.
Those who reach stage five are very strong in their faith, whatever it may be, because they've confronted their doubts and rectified their concerns. Having gone through your "critical" phase, you will be more certain, more committed, and there will be little that will cause you to steer from your course.
Whatever direction your journey takes you, I hope that you will live what you believe. Discover the "truth" for yourself and commit to your spiritual journey. The spirit will guide and direct as you develop your faith and testimony and identify what truly matters and feels right to you as an individual. Your mother loves you, and even if you choose a different direction- as long as you are strong and know it is right for you, I am sure she will be supportive.