Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.
Given the history of a motor vehicle accident and neck pain, there are several possibilities, one being a herniated disc. The vertebrae (bones of the spine) have material between them to cushion and allow for mobility. This material may be squished out. This is called a herniated disc. It can be squished out centrally or laterally. In most people the pain associated with a herniated disc may resolve within 4-6 weeks. A minority of patients do not respond to medical/conservative management and require surgery. Symptoms suggesting the need for urgent surgery include muscle weakness, loss of bowel or bladder control, loss of sensation, and progressive pain.
A test called EMG/NCS can be performed to determine the extent a nerve is being compressed or damaged by a herniated disc. This test is performed by neurologist at most local offices.
Other possibilities include musculoskeletal pain, fibromyalgia, metabolic, etc. Fibromyalagia is another medical condition that leads to whole body pains. Its cause is unknown, but it is characterized by diffuse aches, sometimes GI symptoms similar to irritable bowel, sleep abnormalities, low pain threshold, and other features. It is best treated with medications such as lyrica and neurontin, exercise, and physical therapy. Sometimes muscle cramps are from abnormalities of the thyroid or low potassium.
Less likely causes (based on your history) are fatigue, alcohol abuse, inflammatory myopathy, drug-induced muscle pains, etc.
I would recommend that you discuss your concern with your physician. You will need a detail history and examination to help determine why you’re having muscle pain and to determine if it is related to your neck pain.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
Thank you so much. I've considered it may be fibromyalgia.