Brief Answer:
More information is needed.

Detailed Answer:
I read your question and I would very much like to help you but I am afraid more information is needed. You must understand that headache can be of many types and causes, imagine that only the headache disorders classification of the International Headache Society is a pdf document of 180 pages, let alone going more in depth.

So you should provide some more data such as:

- location of headache
- duration
- onset (was it sudden or gradual over hours/days/weeks/months)
- characteristics: throbbing, pulsating, constant, pressure like, sharp, lancinating, burning etc
- triggering or exacerbating factors: lack of sleep, stress, certain foods or drinks, head position etc
- accompanying symptoms such as: nausea, vomiting, fever, increased sensitivity to light or noise, vision changes, running nose, tearing, eye redness, weakness of the limbs etc, any other symptoms might be useful
- history of previous headache, if yes since when, frequency, whether same characteristics or different, medication or tests done for it.
- other medical conditions or treatments you might be under, family history

So for now all I can say is to try an over the counter pain killer like Ibuprofen. Imitrex which you mention is a drug used mainly for migraine, or some other specific headache disorders, it's not for any headache and if you had some heart or blood vessel condition it might be harmful.

I remain at your disposal for other questions, but possibly with some of the requested information.

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Brief Answer:
Read below.

Detailed Answer:
Thank you for the feedback. It is prudent from you to go see a doctor since the headache is persisting, might be a manifestation of something more serious and require specific tests. Since you haven't provided the additional information which I asked it's impossible for me to add any additional thoughts as to the type and cause of headache.

I hope you will feel better soon.

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