Painful braxton hicks - dehydration?

So I'm 30w 4d pregnant and for the last 7 hours I've been having painful braxton hicks type pains. The pains are definitely worse when stood up and feel like my bump really tightens with cramps and takes my breath away. When I'm sat or lay down they just feel like mild cramps which come and go. I have put it down to dehydration as I've been so busy at work I'd forgotten to drink anything.  Since I've been home I've had over 2 pints of water. Has anyone had braxton hicks through dehydration? What were they like?