even if you have been smoking for a while?

dont smoke.
it kills.

only if you're smoking too much.
but do not take my word for it.
l am not a doctor or anything

It depends. Nicotine can make u dizzy or nauseous. Normally, if u have smoked for a while, this should not happen. But if u did not inhale before & have just started, or u r inhaling more smoke more deeply now, or if u r smoking cigarettes with more nicotine in them, these could cause it.
To stop this from happening, u need to smoke more. Smoke until u get really dizzy, then stop & wait for it to wear off. Then do this again & again, & soon u will be able to smoke a whole one without a problem.