Frequently Recurring Urinary Tract Infections. High Stress Levels. On Antibiotics, Keflex. Serious?

I have had constant urinary tract infections over the last few months. Treatment has been antibiotics, Keflex etc., but I am puzzled by the reoccurrence. It is not associated with sexual intercourse. I am a grandmother and very involved with my grandkids. Stress levels are high as my youngest daughter has breast cancer and undergoing treatment after a mastectomy earlier this year. I am constantly looking after her and her family and have had colds, flu etc as well this winter. My GP has not investigated this further at this stage so I am asking what the next stage should be. I will have to see him again tomorrow as the uti has surfaced again. I am a new patient to him having moved permanently recently to this area. I am worried this may be something more serious. Thank you.