I am feeling hopeless about a-levels

I don't know what to do. I am trying to do biology and chemistry practice papers but I am getting every single question wrong and I am not even exaggerating.
I did really well in my year 12 mocks with 3A* but the more I think about it the more I realise they were just flukes. I don't know what I am doing wrong. I am making stupid stupid mistakes I'm forgetting everything I revised and I feel so stressed. every time I mark a wrong answer I feel my soul just seeping out I am literally... idk what to do anymore

I would say that you are putting too much pressure on yourself to achieve high grades that you did last year. Although 3 A* is amazing, your mental health is more important and putting that first will reflect in your grades. Perhaps take a few hours out take a walk then look over a topic. Rather than sitting and attempting to do an entire past paper pick the questions out that are on the topic you have just looked at. This way you will be able to identify the areas of weakness and then go back over leave it an hour to do something else maybe look at a chemistry topic and then repeat for each one alternating maybe once or twice making sure that you give yourself 10 minute breaks in-between. This way you are revising doing past questions and making sure that you are keeping your mental health above your grades. At the end of the day you can only do what you can do and if that means stepping away for a few hours then that's the best thing that you can do. Also don't be afraid to ask for help from those around you they are most likely in a similar position to you!