From personal experience with TOS, shoulder injuries, cervical and thoracic spine issues, I'd suggest a physiatrist (physical rehab medicine). They can perform EMG/NCVs, facet injections, scalene blocks, etc to try to rule in (or out) the source of the problem and refer you to other specialists - pain management, neurosurgeon, vascular surgeon, etc. - for confirmation and/or treatment. Keep in mind, though, you may need to see a few doctors before you find out that is open to really looking into the problem. The doctors may be quick to call it TOS because you've got the history. If you don't agree, seek another opinion.