my 7 year old doesn't want to go to school

I have a 7 year old girl that has been going to school good and her teacher that she had  was a substitute her teacher was out on maternity leave untill november 1 and she came back and the other day my little girl whined a little before school and then was fine when i picked her up saying she had fun and the other morning was a different story she kept saying her throat hurt and i told her that i would take her to dr and the dr would look at it then she said it wasn't hurting much that she will go to scool the she was saying her legs was hurting then it got time for her to go and she started crying alot saying she didn't like it she  wasn't going then i had to make her get in the car and in her seat we got to the school she was crying alot saying she hated it that she wasn't  getting out we got there i had to take her by her hand and make her get out .I walked her in to the office and she wouldn't go a lady in the office took her she didn't want to go  she was still crying a little.what do i do i need help