How long after drinking your “usual amount” you started to feel withdrawal symptoms ?

I’ve been drinking for quite a while now. Although I’m desperate to stop I’m unable to bring myself to do so. I drink about 400ml of vodka a day. (At most). But I keep an eye on how much exactly I’m drinking. It’s been at least 3 weeks of this amount and now I get emotionally restless and erratic when sober. I notice my fingers shaking. How long was it that you drank the usual before you notice withdrawal ?