Why do I keep smelling bad?

I’ve never dealt with smelling bad down there until maybe late last year continuing this year. It’s like a fishy smell, not nice at all. I used to have a almost sweet smell and I still do sometimes but it seems like the majority of the times I’m smelling bad. Can someone tell me what may be causing this? It gets worse when my period is about to start. My dr says UTI or yeast infection but I don’t want to stay on the antibiotics every single time I smell bad. Maybe a natural remedy? 😫😣