I am 41, female, i am diagnosed with early degenerative changes in c/spine. what can i do to prevent it?

Unless you figured : Out how to stay young forever, not much other than avoid smoking as this is the normal aging process of the spine. The good news that this does not usually present any issue for most people even in advanced age other than some motion restriction keep a healthy lifestyle and exercise.

Prevent DDD: Don't smoke! that is about all that is in your control. The rest is genetic predisposition, and potentially overuse (heavy labor, vibration/heavy equipment, etc.). Remember, ddd is like wrinkles of the skin. It happens! doesn't imply pain. Nothing sold over the counter has been conclusively shown to be preventative. Keep the core muscles in good shape, use good posture and ergonomics at work.