Quit 4 days ago. feel really strange

I feel really strange. I wasn't smoking a lot 4 days ago but since then I havn't touched a cigarette or any nicotine replacement.

My head feels lightweight and it's really hard for me to focus. I heard you might get dizzy and so on while your body "goes back to normal", but I'm rendered completely useless by this. Just making this reddit post is difficult for me.

Anyone experience anything similar and how long can I expect it to last?