5 year old school problems..not sure where to post

I'm looking for some advice. Last year, my daughter was in 4k. It was a full day twice a week. The entire first half of the year, she cried every time I dropped her off. However, half way through the year we were able to get it under control. Fast forward to this year.. she started kindergarten. She cried the first week, but after that, she was excited and happy to go to school, no tears. She's doing excellent in school, well behaved, reading on her own, very social and has lots of friends. She's been having a great time! That is, up until Thanksgiving break. They had off for a week, and started back last Monday. Every day since then, it's been crying, fits, stomach aches (only complained about when we get to school and it's time for me to leave, not mentioned anytime else. We also went to the doctor last week and all checked out fine) and her asking me if someone can work for me in case she needs to come home. I reassure her, tell her I'll be there if she needs me. I've tried being understanding, I've tried being firm, I feel like I've tried everything. I tried implementing rewards (which worked for one day last week, we had a smooth dropoff with no tears) and I plan on sticking with it, and I don't expect instant results of course, BUT OH MY GOSH IT IS SO HARD. I leave the school feeling terrible every morning, and helpless. Her teacher says she's always fine after the first part of the morning, which is reassuring, but it breaks my heart having to leave her like that. I have a pretty solid feeling that she's having some anxiety problems (I suffer from it myself) but I'm just not quite sure how to help her at this age/point. I guess I'm looking for any tips or advice to manage this until we get it under control. Of course, they have another week off for christmas soon and I'm just worried it will be even worse after that break. Thanks in advance for any advice.