Hello ! Thick yellow sputum is suggestive more of bacterial infection for which you will need the right choice if antibiotic. You can empirically take a course of Tab. Amoxyclav or Tab. Azithromycin along with tab. pantoprazole. One way to differentiate whether it is viral or bacterial is to go for a complete blood count with differential counts , and blood C- Reactive protein assay . However in your case it is rather cost effective to take a course of antibiotic and look for the improvement , rather than spend on these tests. You can get a sputum culture sensitivity done before starting antibiotic as this test tells which organism has caused your Infection and what antibiotic will act against. This test is also not mandatory . Along with medications, do warm saline gargle and gargle with betadine solution (after diluting few drops in a glass of lukewarm water) thrice daily. Consume only warm fluids.