Struggler, these early three weeks can be tough. You've made a smart move in choosing to be free of the chain of addiction.
I'm seven months down the line now and can honestly say it does get so much easier as long as you don't fall into the trap of listening to the addiction and going for the just one. It would only end in a vicious cycle.
I was told when I quit that the first three weeks were hell, heck and WTF weeks respectively.
Day 13 is huge, you should be massively proud of getting here. All of the symptoms you have are absolutely typical and common with the early experience of other quitters. You are having them because you smoked not because you quit. I can tell you that I had similar and improvements were gradual. I promise you will feel better, but it takes time to reflect and can be a good idea to write down your experiences so it is easier to look back on and see the difference. Today is another day just like the previous 12, get through it. You get through today that's another one you win and the addiction loses.
Stay strong, stay with us. Rant, ask questions. Be here with us and let us help you get through today and then tomorrow and the following day if you want.