Pressure in left temple, behind the eye and down the left side of head behind the ear. tight muscles in neck. allergy meds having no affect. ideas?

Not allergies: Sounds more like tension headache- talk to your primary care doctor about this

Head pain: This could be a headache condition such as a muscle tension headache or a migraine, but much more detail is necessary. Other possibilities might be myofascial pain from clenching or grinding your teeth. Sinus/ allergy conditions would be less likely based on the information provided. Lastly, other conditions such as trigeminal neuralgia or temporal arteritis could be considered. See MD for help.