Hi, i have just had my lunch and also had a cigarette, now i feel really sick, shakey and i am sweating.

I suspect there: are times when the effects of nicotine are more intensely perceived. It may be that when one's metabolism is occupied with certain functions of digestion that, and not necessarily every time, nicotine side effects are stronger. Or after certain foods. Use common sense and experiment. Avoid smoking right after eating and see if things normalize. Better yet: work diligently toward quitting tobacco!