I have recently been diagnosed with IBS after a period of constant nausea, pain, constipation and diahroea. During this time I had a raised temp and was given doxycycline and clarythromycin which made my symptons much worse. I later had cystitis ( I have recently been told I may have interstitial cystitis) for which I took trimethoprim. I actually vomited with these. my cystitis has become worse and I think I'm going to med more antibiotics. Can anyone suggest one that is less of an irritant to the gut. I am allergic yo penicillin.