HI, My Daughter Is 6 Yrs Old And She Has

HI, my daughter is 6 yrs old and she has been feeling nauseated and sick everyday , for a couple of weeks now, in the morning when she gets up to go to school and when she comes home from school, she's still complaining that she didn't feel good at school. she looks pail, and just today she got a little fever on top of that. I'm just wondering if you can give me any advice what it could be?