So sorry for your loss as well.
No, pressing the "m" button just sets the start of a new cycle, this wouls ask you to test based on previous months, so if you had a false high you miss you high the following month. *Resetting it deletes all previous cycles, so if you have false highs / no highs this would avoid these results distorting (but you have to use 10 sticks each time you reset).
Actual resetting is covered in the back page of my instruction booklet (which you can down load from the Clear Blue website).
Only reset if you think have a false high though, i kept a diary with my cycles last time from before we started trying so I'm going to compare my first month to these. *If they are off i'll reset again, if they are in line (give or take a few days) i'll leave it running even though we won't start trying. I think we'll wait until at least Sept/ Oct so i can start to recover emotionally, I'll then take it from there. *Good luck xx