I don't feel well, I'm very anxious and stressed, I even lost my sense of taste. My face feels very hot I don’t know why!

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Tomorrow is my appointment with the dermatologist, and I can't stop thinking that I might have skin cancer, because of the peeling mole. I am terrified and very anxious, I cannot sleep, and the feeling in my heart continues to beat, like a frightened little rabbit.
What do I do? I want to think positive, but I can’t! I'm just afraid

Take a few deep breaths! Great that you are seeing an expert doctor tomorrow who will be able to help you and make a plan. It's ok to be nervous but not long to go now. I would pass the time now by getting up and getting my clothes ready for the appointment, deciding how I am going to get there, and getting a notebook/ piece of paper to write down what I want to say to the dr about what's been happening and what i am worried about

@Sorrento79 Thank you for your support. For a moment I thought not to go because of my extreme fear. My mother will go with me, but I feel like I'm alone even if she's by my side, because she doesn't take my anxiety seriously. I just wish I had emotional support, I don't know what to say to her to make her understand me. I want to not feel like I'm alone in this!

You are not alone, the proper health care professionals will be there to see you and sort out what is necessary. Definitely go tomorrow and definitely say what you are worried about. If your mum makes you feel awkward doing that just have her wait outside and use your notes to prompt you to tell the dr your concern

As above, write down a list. That is a really good strategy lots of people use when they feel anxious about going to the doctor.
I'm actually also wondering from what you say it sounds a little like your immune system is stressed, which can cause symptoms of anxiety. Lots of things can stress the immune system, from covid to health conditions and external factors. Hopefully the doc appointment will shed some light on things for you. It might also be worth separately having some CBT to try and understand what causes stress for you and things you need or can do to stop it affecting you.