Another one echoing to see a GP. Or, it sounds like you work in the medical field, have a quiet chat with one of the docs you trust. I certainly wouldn't be taking anti's without a current prescription. I find it odd that you were instructed to only take 3 days worth the first time - I've never heard that one! Have you tried cranberry juice in the meantime? It can help with UTI's. Taste's foul but works.