I am in the same boat lilacclaire. Well, I gave up smoking 4 weeks ago and look dreadful, and have been ill virtually ever since. I have had lots of spots etc.
I have my own theory as to why this happens:
Smoking has all kinds of different effects on body chemistry, so if you have smoked for a while, it will take time to adjust. While it is going a little bit haywire, you need to bear with it.
For example, it dries out the skin, so perhaps the body was previously over-compensating for that by producing excess oil. Now that the smoking has stopped, the body needs time to reduce the oil production. Initially you might feel and look worse. However, having given up before, I know that after a couple of months, you will definitely look at least 5 years younger .
Also, nicotine is apparently a bactericide - it kills germs. So in the early stages after giving up, you can be more susceptible to getting ill.
Hope this helps - wait a while, eat wisely, drink water and honestly you will notice the improvement eventually.