a new med/mother's milk comes out every couple of years with more and more info.
kara has nailed this info so perfectly for you noah'smommy

hope you get rid of your migraines soon. have you figured out is you have any food triggers for them? also, have you tried chiro adjustments?
as for the meds, percocet, tylenol 3, vicodin, etc. (depending on the doc usually) are what are prescribed very often after a mom delivers, so yeah- they're fine for nursing with. phenergan is a pretty safe med also, but like kara said, don't overuse, or it could impact supply.
also, there is a supplement out called (and i know i'm gonna spell this wrong, cuz i havent bought it in awhile) petadolex. it is a migraine preventative. worked for dh when he remembered to take it at least most days of the week. you may want to look into that as well.