If you can't tell yet then you don't need to worry about whether it is or isn't. You'll know eventually as your symptoms won't go away, they'll get worse...oh and a little person will pop out of you...YEY, congrats!
Seriously though, I'd had BH on and off for days so wasn't sure myself till I realised my BH would usually stop after a few hours and six hours in these tightenings were getting more uncomfortable and not going away, so not BH but labour.