I also think it's just our body's response to extra hormones. You sound just like me though, and I'm having a girl! With my 1st two (boys), I was nauseous a little bit in the mornings, but the rest of the day it was fine. That happened from about 6 1/2 to 12 weeks. This time- I was nauseous all day long, and it lasted from 6 to 16 weeks. I'm 20 weeks now and still feel icky on occasion. So for me, more m/s meant girl.
Oh i so hope this is my girl! I am 14 weeks tomorrow and still feel icky! I know in the end all this m/s will be worth it