Go see a doctor.

That said, I frequently end up with a lot of congestion in the form of post nasal drip, coughing, sinus and ear pressure after being sick (and sometimes for no reason at all it seems).

My ritual:
1. Afrin nasal spray 2x per day for 3 days on, 3 days off for 2 weeks.
2. Mucinex DM 2x day for 2 weeks.
3. Usually paired with antibiotics 2x per day for 2 weeks as prescribed by my ENT.

Steamy hot showers with a warm wash cloth over my face doesn't hurt either.

If, after 2 weeks I still feel congested (usually not), rinse and repeat for 2 more weeks.

Good luck.

You'll be amazed how much better you feel once things start draining.