For over one month have had nausea, sore throat (mild) and headache. Per ent, not sinus but gerd? Should I see GI doc?

Try OTC meds first. Depending on your overall healthy and if you aren't already on a number a medications, you could try over the counter (otc) medications designed to treat gerd such as ranitidine (zantac) or a proton pump inhibitor like Omeprazole (prilosec) or Lansoprazole (prevacid). If you do not get relief or if the meds stop working, a visit with a GI doc would be reasonable.