What Causes Headache And Nausea While On Flucloxacillin?

Hi, I have been taking Flucloxacillin for a eye infection and only have today and tomorrow left from a weeks course. Sunday night I started with bad headaches and I am feeling constantly sick (but not sick), very tired and I have to sit with the light out. I am female and 25. Does this sound like it may be the anti-biotics causing me to feel like this.