What Causes Lower Back Pain Along With Nausea And Intermittent Diarrhoea?

I am 58 female and usually fit and healthy of normal weight but with mild asthma not on routine medication. I had sudden onset diarrhoea and vomiting 2 days ago lasting all day with rapid heartrate (98 when lying). I can now eat and drink and have rehydrated but have lower back (kidney?) pain and feel nauseous. I have intermittent diarrhoea but no vomiting. Should I see a doctor/take antibiotics.