Hi,
Agree with talking to the bfn. kellymom has some useful information about migraine medications and breastfeeding, and it would probably be worth talking to your doctor regarding safe medications to take while breastfeeding, although be aware that some doctors are fairly clueless about bf and pretty much think all drugs are bad, so go prepared.
There is another article here which talks about the effects of sumitriptan (active ingredient of imigran) on breastmilk. Cut&Paste:
"5. What is the latest about taking Zomig, Sumatriptan, Maxalt:
Sumatriptan, trade name for Imitrex, is a newer anti-migraine medication that is closer to the serotonin reuptake agonists. It has been studied during breastfeeding and a small amount does get into the milk. The total amount of drug found in the milk after a single dose was very small. This concentration in milk corresponded to an infant exposure of only 3.5% of mother's dose. The oral bioavailability is only 14%; thus, the infant would only absorb 0.5% of the mother's dose. Thus, it is not thought to be a risk to the suckling infant. The milk half-life is 2.2 hours. The concentrations in milk are very low."
Sumitriptan has also been approved by the AAP (American Academy of Pediatrics) for use in breastfeeding mothers, see list here
I would also add that I used to suffer from regular migraines (aura, nausea, only thing that I could do was lie down in a dark room), and I've only suffered from 2 since starting bf (DS has just had his 2nd birthday). When I did get one, I followed my usual lie down in a dark quiet room thing and fed him lying down in the dark (he was still fairly young and happy to cuddle up to me, not sure that would work now...), and handed him over to DP when the feed was over.
Hope that helps.