I agree with whisperwolf, you need to inform your doctor that your current acute treatment plan is not working.
I also agree with whisperwolf that codeine is not usually the ideal acute treatment for a migraine attack as it is not a first-line treatment. Also, as whisperwolf pointed out, it is possible that codeine can cause rebound headaches, and although it is much less likely that an opiate product will cause a rebound headache than most over-the-counter pain medications, the problem is that codeine is almost always mixed with a medication such as acetaminophen (as is the case with T3s) or an NSAID, and these types of over-the-counter medications will cause rebound headaches.
Triptans are the first-line acute treatment for migraine headaches and they will not cause rebound headaches. Some people cannot take triptans for specific medical reasons. This may be why your doctor prescribed you codeine instead of a triptan, although there are still other medications that may be more effective at treating migraine pain than the codeine is, so please talk to your doctor.
Also, if you have a severe migraine headache that lasts for over 72 hours straight (3 days straight), many doctors will consider that an emergency situation and when I have a migraine that lasts for over 3 days straight I will go to the Urgent Care Centre or the Hospital Emergency Department. If your headache is severe and continues for more than 72 hours straight (3 days straight) and you cannot immediately contact your family doctor, then I would suggest seeking medical treatment from a walk-in clinic, an urgent care centre or the Emergency Department.
Call your doctor and tell him that your meds are not working anymore. Codeine for migraines are not a very good drug because they can cause rebound headaches. There are much better choices out there :)