12 days ago, i started having left-sided back, side and chest (bottom of breast to bottom of rib cage) paresthesia. pa-c ruled out shingles. what could it be?

Go up the ranks: See a doctor to find out if you have a problem at the level of the upper thoracic or cervical spine. Imaging (e.g. Mri) may be indicated. Do not be satisfied with a pa's assessment. Seek advice from a higher echelon, as it were. Symptoms are treatable. Cause may not be benign. There's no substitute for seeing an md/do face to face and getting a thorough exam and thoughtful evaluation.

Spine vs Neuralgia: Although shingles may have been ruled out, there is a small possibility that you could have had the shingles without the pustules. This can also result in post herpetic neuralgia. Other possibilities include a thoracic disc herniation or rib displacement causing intercostal neuralgia. If this does not resolve n the next 1-2 weeks. You should seek further medical advice and care.

Myofascial Pain: Your pain could be from shingles that never broke out in a rash, but before you accept this answer, touch and look for a tender knot in a rope of muscle that runs down your side, a few inches below your arm pit. If you find it, this knot could be causing your symptoms. Push on it hard an squish it, your symptoms may improve as soon as you do it. www.blatmanhealthandwellness.com.