Breakdown Photography A level

So I have been pretty confident in Photography so far, my teacher has been saying my work is great and keeps telling me my ideas have great potential. I've been on target for a grade B for a while, but today I got a feedback slip that told me my work is C/D. I saw the grade and honestly I just lost it. At the top of the slip it said "uninteresting theme", she could have told me she didn't like my theme when I started the course a year ago... But no, she's been telling me how much she likes my idea just to tell me NOW that it's "uninteresting". I basically just held back tears for an hour, questioned all my decisions for the future and burst into tears in the toilets afterwards. It was really embarrassing. But yeah I don't know what to do, I can't change my theme now and honestly I was really proud of my work up till now. My teacher went over my prep work a week ago and told me that to improve, all I have to do is little things like change the font size of some of the text and make some bits darker but literally that was it, other than that I've been told my work is fine. Now I'm scared I will be predicted a C or even a D, I might never get an offer from a University... What's making me upset is just the fact that my teacher was never honest with me before, she should have told me to change the theme a year ago if she thought it was "uninteresting" and now I don't know what to do!