How would you distinguish between a new versus a chronic infection in your vagina?

Timing is everything. If it is your first time, and you have new symptoms that you have not had before, then it is a new problem. If you have had similar symptoms in the past and you have been treated for the same thing in the past, then it is chronic. To make matters more complicated, between new (acute) and chronic, there is sub-acute. Either way, it is time for you to call your doctor!