unsupportive teacher

I really don't know what to do!
One of my psychology teachers is so unsupportive and criticising of me and my work, but isn't like this with anyone else!! Others in my class have commented on how she seems to treat me compared to everyone else and my mental health is getting SO bad as a result (
In Year 12 she told me I was going to fail my A-Level because I got a D in one end of topic test, and when I tried to explain to her that my mental health was really bad that week I just had to prioritise that over studying, she told me that wasn't a good enough excuse and my grades are more important than my mental health!! I then asked her if I could go to the bathroom (she said yes) and then went and told almost every teacher in Sixth Form that I walked out of her lesson, which is not true at all!
At the start of Y13 she seemed much better, but recently she's started criticising my work again and implying I'm stupid We had a mini mork on Cognition and Development, which is by far my weakest topic, and after the exam I was complaining about how hard it was, and then she went and told me that the questions were really easy... Obviously this didn't help me, and made me feel 10x worse about the test, which I was already feeling rubbish about!
Additionally, she's just been generally unsupportive and criticising of my in-class work, and I'm really starting to lose faith in myself. I now absolutely dread going to her lessons, and have had panic attacks over the sheer thought of school - even on days I don't have her lessons.
My Mum emailed my other Psychology teacher (who also happens to be the Head of Psychology) on Thursday night about this, and I feel like he may have misinterpreted the situation as being short term/one off, as opposed to a long term problem. I'm thinking I should either send him another email, or speak to him about this after our lesson
Does anyone have any tips on staying positive when you have teachers dragging you down, as well as how to speak to the Head of Department about my teacher and what she's doing?
Thanks in advance )