Sounds like pre-labour to me - my first labour was like that - started early Friday morning and DD was born on Tues night.

It could be gastro but sounds more like pre-labour. If your body is ready to go gastro could also trigger labour (having the runs can cause your uterus to start contracting).

Just keep an eye on your temp . . . if you start to get a fever or anything go and get checked out by your health care provider. Try and keep up your fluids and keep track of whether you think you are keeping them down. If you seem to be bringing up all fluids, then you need to also call your health care provider.

Try and get some rest . . . if this is it, rest can only help. Good luck