Gastro made my body go crazy. Advice?

A post for the ladies out there or learned men or medical professionals... I got a bout of Gastro on Thursday in the late evening (it's now Sunday). On Friday, as I was in hospital, I didn't take the pill. I picked up where I left off on Saturday. I noticed some cramping which I thought was part of the Gastro, but today my monthly visitor has arrived. I last had it a week and a half ago!

I take a tri-phasal contraceptive pill and was in the section after the lactose pills.

My question is, does anyone know which phase of my pills I should take to STOP my visitor? Or keep going as is and hope it stops (which I would rather not). Stupid body!!!