Hi MrsS,
Usually a really bad headache can be relieved by over the counter medication quite quickly.
This isn't the case with migraines and cluster headaches.
My older daughter has suffered with migraines since she was seven, and has learned to recognise when she is about to have one, and take precautions. Usually, in her case, a full blown migraine, with all the associated distress, can be prevented with rest and medication.
Cluster headaches are somewhat different. They are severe and usually affect one side of the head. The sufferer will get several of these headaches over a period of weeks or months.
Whereas, with a migraine the severe headache may occur for up to 72 hours maybe once or twice a month.
I am talking very generally here about these conditions, and if you suffer from severe and persistent headaches, you should see your doctor.
In my daughter's case, the doctor ordered a CT scan to rule out other serious possibilities before diagnosing migraines.
There is a wealth of information on the internet, and I found a couple of pages on MSN that I thought might be a starting point for information for you:
MigrainesCluster Headaches