I always feel the contents of my food up my throat after eating. Is this sure sign of gastric reflux?

Probably LERD w/GERD. Exposure of the vocal cords to stomach acid & pepsin will result in inflammation of the vocal cords (as is also often seen with acid regurgitation). Acute laryngitis may result, but watch out for chronic hoarseness, throat clearing, airway spasms, bronchitis, an asthma-type presentation, and even a higher risk of throat cancer. Please get evaluation & treatment for your laryngo-esophageal reflux.
Reflux. This can be a sign of esophageal reflux but does not make the diagnosis.