4.5 weeks morning/ whenever sickness

so for the past half a week if I smell anything I don't like my stomach flips and my mouth goes all full of saliva and I'm desperate to be sick. was actually sick for the first time yesterday. Everything I read says from about 6 weeks on.......hmmmm I've been tracking fertility so definitely only just 5 weeks today. Please tell me it's just an early start n it's going to go away soon! I'm a teacher and the kids farts are killing me - I walked out the room today it was so bad!