What to do about my job? please help?

Ive been in a job for nearly 2 months, and since the beginning i've been close to wanting to leave due to many reasons. I have forced myself back week after week, but since more occurances have happened I really want to leave as it has pushed me to tears at work!. Theres only one other person who can do my job, id love to be out now, but dont want to leave them in lurch , but honestly the thought of staying reduces me to tears. I fele so trapped. Ive no contract, but feel i should give a week notice period out of courtesty but working there a week fills me with dread as it will be made hell.im so confused and know i should fele lucky to have a job, but ive literally pushed myself as far as I can but its making me so miserable. Also do I put this job on my future job form or is it not worth the agro being asked why I left etc? Thanks xx