I had sex when ovulating twice, on what it says are my most fertile days. 5 days later and I have started to feel 'flu-like', dizzy & sick? Any advice?

The symptoms. Of pregnancy do not usually occur this early. It is possible, however, so I would recommend a pregnancy test if your period is late.You may be getting the flu or you may just be worried. Anxiety can cause physical symptoms. Get plenty of rest and fluids. Schedule an appointment if your symptoms worsen.