My teacher does not help me, and l do not know who else to go to?

l am doing an NVQ in Business and my assessor is the worse l have had by far. l answered every single questions on my portfolio but everytime she marks it, she does not explain them clearly enough, she just puts a big question mark next to it, or type 'rethink this question' or 'research', which is what l have done three times! She shouts at me if l do finish going to the loo quick enough, when l explain something, she ends up telling me how wrong l am. l do not know what to do! Can l complain about this? l would feel like l am being unfair but what she is doing is not helping me at all.