i really would not use it at 33wks!! i tried it and i did get braxton hicks but that was all. no labor.
also with my second baby i was measuring really big. i was scared about having a big baby. im a small girl... 5'2, was 8stone before getting pregnant... and also i had jsut turned 21. so my midwife said i would not have a big baby. i went into labor, the pain was real bad, worse than with my first... anyways.... i pushed out a very healthy 9lbs 12.5oz baby boy!! my midwife told me your body will never make a baby that is too big for it to deliver. so dont worry that you look big, your body is deisnged to do this! it knows what its doing