You also want to finish before you start your thirty - sixth week of pregnancy. (verywellfamily.com)
It starts somewhere between the fourth and sixth week of pregnancy and is therefore one of the first pregnancy signs. (pregnancy-info.net)
The APA goes on to add that morning sickness (nausea and vomiting) usually begins around sixth week of pregnancy, and seems to stop after the 12th week. (romper.com)