now on Trimethoprim

Went to drs today as back and legs ache so much and they seem to think i have bladder/kidney infection as there is red and white blood cells in my urine so have been put on a course of trimethroprim and  to go back in a week,has anyone else been on this and have you had any reactions as it carries a interaction warning am on 6mp and is ment to increase effects considerably.

I am back at drs next week to make sure all is going ok have not got GI appointment untill may will just see how it goes fingers crossed.