In my first pregnancy I started slowly developing symptoms from around 6 weeks, until they really kicked in at around 9 weeks.
I'm currently 6 weeks and 4 days pregnant with my second, and have has really sore breasts, feel super tired (trying to go to bed early when not working late) and a bit of nausea after breakfast until I have eaten my lunch, then feel loads better in the afternoon. Until later when I get tired and I feel nausea again.
Some people don't experience any symptoms, maybe you'll be one of the lucky ones.