Hi I also suffer from this, there was a previous thread on this, can't remember what it was called.
Someone suggested it maybe mittelschmertz syndrome - if you find it is particularly bad at mid cycle some women suffer from this when ovuating. I also have endometriosis which I think may aggravate it. Look it up on google.
It is nothing to do with what I eat/drink or don't eat, and it doesn't make you need the loo. I know period type pains when I feel them.
I just avoid doing races at that time of month now, having been ambulanced off a 10k unable to walk let alone run, and then an hour later being fine, and feeling a complete fraud.
I found it very frustrating until I worked out what it was, everyone kept suggesting dietary changes but I knew it was not related.
Hope this is of some help.