I don't think you need to go on medication to be happy. I think your job makes you miserable, and that itself is what you need to change to feel better. Staying in a job that makes you miserable isn't good for your health.

You mention that your dream job is hiring and that you have their phone number. Can you call them up, set up an informational interview with them to find out if it is a good fit for you?

If it is a better fit for you, then you may want to let your boss and coworkers know. If you truly have a good relationship with them, then they will understand that you found a better opportunity, and will support you. As Shakespeare said, "to thine own self be true."