How soon is too soon to quit?

I started my first real job the first week of September (graduated college last May). It’s a finance job at a well known company. Basically it was advertised to be completely different than it actually is and I’m MISERABLE. I dread every single day and can not imagine being here much longer, but it’s only been barely over 4 months. I know it would probably look terrible to leave a job after four months. Do you think it’s too soon to start applying for new jobs? Will companies take me seriously?

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