How long will my tension headache last roughly? how can i reduce it, and what can i do in the future to prevent it?

Neurologist: There are many options for headache treatment and each person is unique in how they respond to therapy. I would recommend seeing a neurologist, specifically headache specialist.

Difficult to say: Tension headaches generally should last only several hours, but they can last more. The important factor is to determine what your triggers are, such as hunger, stress, bad posture, eyestrain, etc. There are medications, such as antidepressants, that can help prevent the headaches. Managing your triggers can also prevent the headaches. Talk to your primary care provider.