Pregnancy migraines/headaches

Hi there! Currently 18 weeks preggo and I used to take imitrex for migraines but now I can hardly take anything it seems! I have Tylenol but it only helps a teeny bit! I'm a nurse and working 12 hours with a massive migraine totally sucks! Anyone have any recommendations on what to take? My doc says she'd rather me have caffeine than anything! I don't get them everyday but once it comes, it's BAAAAAD. Thanks!