Had only a low grade fever, mild sore throat for the first 2 days of cold. no voice used. then yesterday i talked for 2 hrs and boom!, hit with a debilitating sore throat (getting better), and today a 38.7 fever. is this because of using my voice?

Usually not that: Sore throat can be strep throat (antibiotics are needed), a cold or influenza (Tamiflu antiviral may be used), or less likely from some other cause such as allergies or irritants. Usually, a person sees the doctor if symptoms are bothersome, recurrent, or don't go away quickly (to see if antibiotics are needed). The doctor can examine, and maybe do a strep swab.