It is a possiblitity that the tests were done too early. Pregnancy
tests detect the levels of HCG
and the urine tests can vary in the amount of HCG that they can detect. Some detect small amounts and can pick up pregnancy earlier than others. You can repeat it to see what the result is at this point.
Some women can experience light bleeding in the early part of pregnancy as the fetus attaches .
There are other causes of nausea: motion sickness
medication induced nausea
reactions to food/odors
If the pregnancy test is negative then you need to consider going to your doctor for a check up to rule out other causes.
I hope this information is helpful to you