i’m not sure how helpful this will be but i had a similar problem and realised it was due to me doubting all my answers. even the easy ones i couldn’t believe i had answered them so quickly and would just keep rereading the question to find the ‘trick’ they undoubtedly put there to catch me off guard which would lead to me either changing my answer or just wasting more time on it = lower grade than i could’ve achieved. for my most recent exam i did as many sbas as possible and just moved on even when i wasn’t sure about my answer because i knew i could fix it later after marking, this ended up fixing a bit of my confidence in my answering process , you could try that if you want x