I so sorry for you Karima and for your problems your words made me cry but don't say that you can't help your parent and there is no one who can help you becose there is Allah who will help you to be a docter and to help your parent
i'm sure that you will secceed and you must remember that our God will help you
finaly you must always say Problem i have a big God and don't say God i have a big problem