I've been ill with a cold and bad throat, my mucus has now turned yellow and my heads gone really heavy and hurts to look down what does this mean?

Sinusitis?: These symptoms are typical for sinusitis, i.e. the cold involving the sinuses (air chambers) around the nasal cavity. Sometimes it means a sinus opening is blocked, and sometimes it's a bacterial infection on top of the initial cold virus. Try a decongestant nasal spray (look for active ingrediate oxymetazoline). See a doctor if that doesn't help, or ASAP if severe pain or high fever.