Well every woman's body is different. Some women never experience morning sickness at all.
When I first noticed I was 2 weeks late, I went directly to the store and got the EPT digital test. I had that gut feeling that I was. I called my partner to inform him and brought the tests over and waited on the results together. Surprise-it read out 'pregnant.'
I didn't begin morning sickness until about 8 weeks in (Which would have made it about 6 weeks after I found out)
The biggest symptom that lead me to believe I was pregnant was fatigue. I was tired all the time. Didn't matter how much sleep I got.
Some people don't spot at all either.