Yesterday I Thought I Was Having Sinus Congestion..., Took A

Yesterday I thought I was having sinus congestion..., took a CVS brand, is sis pill. Last night opened up blowing nose and some congestion....some cough..... Switched to Robitussin DM.. Today in morning, felt pretty good. Blowing nose, etc! Tonight I hit a brick wall! Very stuffy nose can't blow it and slight cough. Help