Candidiasis (vaginal thrush). Does having daily sex make it better or worse?

Often worse. The "headquarters" of yeast, usually candida albicans, is in the bowel. Vaginal treatment is inadequate. You need to see a physician who is familiar with the diagnosis of "yeast syndrome". Yeast in the bowel feeds on sugar so there is a strong association with diet. Sometimes fermentation in the bowel gives rise to "growling and bubbling" that is even audible.