What Are The Side Effects Of Champix?

I am planning to start taking Champix to quit smoking. I also take tablets for blood pressure - Concor 5. Champix has been recommended to me since my sperm count has fallen and the gynac wants me to give up smoking - my wife and I are planning a second baby. Pls tell me if Champix has any side effects. Is it useful? How long shud it be taken for and what shud be the doseage. I smoke 5 cigarettes a day.