Symptoms start to ease at around 10/11 wks as the placenta takes over and begins sustaining the pregnancy. I wouldn't worry too much, unless you start having cramps, bleeding. If you are considered high risk then I would call the OB and see if he/she feels it may be necessary to come in for an US.
With my girls (3) I barely had any symptoms through out my pregnancies, they came and gone.
As long as there is no bleeding I wouldn't worry pet. Fingers xed! Good luck!