Just finished antibiotics for sinus infection but now i feel worse, could the infection have spread somewhere else now should i go to the er?

Cannot diagnose: These days sinusitis may not always require treatment with antibiotics. Once having been treated, if it was effective, that will not necessarily reduce the symptoms which may be due to continued blockage of drainage and accumulated inflammatory products in the sinuses. Complications are numerous. See an ENT doctor. Not an er issue generally.