Do you believe you might be suffering from insomnia? Perhaps something to help with sleep is in order? Your not sleeping much but very tired, this can cause pain, fatigue and effect concentration and performance. Did the sleep issues begin when starting the meds? The pain start after?

Do you have FMLA? If not, you might want to talk to your doctor about getting it to protect your job while you get this straightened out. FMLA can help with absences and also require the company to give you reasonable accommodations so you can stay at your job. They can reduce workload, stress, allow you more frequent breaks, etc. it would be terrible to take a job with less responsibilities and pay, then suddenly find what works for you and have lost your senority at your current company.

However, if you feel that switching jobs could be a solution, definately keep exploring that. But you need a year on the job to qualify for FMLA.

I'm sorry you are suffering and hope you feel better soon. I've also been advised to never make big dcisions while in a mood episode. Good luck.