You can have mild to moderate cramping (similar to menstural cycle cramping), backache, headache,
fatigue, nausea, vomiting, fluctuations in appetite,
constipation, diarrhea, mood swings, breast tenderness and/or frequent urination. However you can also experience none of this. If you don't, it doesn't mean the pregnancy is doomed to fail. Same as having these symptoms - it doesn't mean all is well.