Dr suspects Supraorbital Neuralgia but how do I know it's not just a sinus issue? I'm not draining anything color just white thick mucus.

Imaging scan. One easy way to tell is to do a CT of the sinuses (MRI can also be done but might be overkill). If there is significant inflammation or buildup then sinusitis can still be a possibility. However, if you are a person with issues of chronic sinusitis, then the CT of the sinuses may not be very specific and may indicate a chronic non-symptomatic finding.