For the past year, i've been having pain on left side of my head. recently, i've also been having left temple pain and behind left eye. any thoughts?

Headache; sinusitis: Head pain with pain behind the eye can be due to a few things. By far the most common is a change in the blood flow to that area in the form of a migraine or headache. Since sinuses surround the eye, it could also be sinusitis. Rarely a mass (benign/not cancer; malignant/cancer) can cause such symptoms. Your md will be able to examine for other signs and may suggest a scan if needed.

Headache: It is possible you have migraines. The majority of patients report pain mostly in one side, throbbing, associated with light sensitivity and nausea, could be aggravated by movement and improves with resting. Frequent headaches could result from frequent use of medications. Responds to diet and adequate sleep. I suggest to check with your doctor for adequate treatment. Hope you feel well soon.