just a suggestion: i would try to use more than one reality check technique. i use the fool proof nose check. it hasn't failed me yet.

i'd also like to add that during my first lucid dream, i became lucid using the nose check. i started to question being in a dream so i tried the finger through the palm check and it didn't work (i redid nose check and was dreaming). sometimes reality checks don't work. maybe thats why?