Alternating nasal congestion that worsens at night is often linked to the body?s natural nasal cycle and increased blood flow when lying down. Since antibiotics didn't help, your symptoms are likely inflammatory rather than bacterial. For relief, try a generic steroid nasal spray (such as fluticasone or mometasone) or an antihistamine spray (like azelastine), which reduce swelling. Saline nasal rinses before bed can also help. Avoid decongestant sprays (like oxymetazoline) for more than three days to prevent rebound congestion. Consult your doctor before starting.