It's also normal to have *some* yeast, if that helps. Most people have some living on their skin; it's just that in dark, warm, moist places it can overgrow until you have too much and it becomes a problem, or broken skin can introduce it under the skin where it isn't helpful. So you don't have to worry about nuking every last one, just getting the colony back under control.
The only douche method I know for treating a yeast infection is, counterintuitively, not about killing them off directly at all - it's to use live culture lactobacillus yogurt (and eat lots of it, as well). That particular bacterium eats yeast, so if you can tip the balance in its favor... It's also among the beneficial bacteria most commonly found in cis vaginas, so it's not that you'd be introducing something foreign and later unwanted; this will help establish the healthy natural flora you want down there.
As always, though, check with a doctor first.