I Have Been Diagnosed With A Staph Infection And Have

I have been diagnosed with a staph infection and have been prescribed Keflex capsules 500mg, two capsules twice daily. I have been taking them since Wednesday night (today is Friday) and a short while ago I experienced massive stomach pain and extremely bloated stomach - have toileted - a small amount of loose faeces but the pain keeps coming in bursts and is extremely debilitating and painful and stomach is still grossly swollen. Should I return to doctor (his surgery is not open at weekends), should I keep taking tablets or cease taking them?