I had absolutely no pre-labour: my waters broke at 38 +2 weeks and contrax started a few hours later 3 mins apart....

in retrospect there were some signs: i got very emotional in the week before. i didnt want to move anywhere and walking was the pits. then the day my waters broke i went a bit manic and tried to clean the house top to bottom and dig a new garden bed...

i hope that it happens soon for you and you can prove the ob wrong and get your vbac!!