I am not sure what is going on, but I am concerned that these symptoms have been occurring regularly now for as long as 3 years. I would strongly suggest that you go see a doctor
about this issue, if you have not done so already. You could start with a complete physical examination by your primary care doctor
Pain up and down the entire left side of your body is unusual. There are several serious conditions that could cause this, including a problem in your neck that is causing compression of multiple nerves or the spinal cord. It will be important for your doctor to perform a neurological examination, looking for any objective evidence of weakness or other neurological symptoms which might be clues. Make sure to mention if you have any other symptoms like numbness
or tingling and whether you have had any history of trauma to the head, neck, or spine.
Sometimes, pains like this might not be caused by a specific neurological problem but, rather, may be a reflection of a more body-wide problem like fibromyalgia or a pain amplification syndrome.
Your primary care doctor will be able, after the physical exam and interview, to point you in the right direction in terms of additional testing or referrals, as necessary.