Managing Migraines at Work

Erin
So a couple years ago I was diagnosed with Chronic migraines. Meaning I have a migraine that pretty much takes me out at least 15 out of the 30 days a month. I'm talking nausea, auras, vomiting, the whole nine. They've gotten better and are no longer chronic but I still get them often. I'm at a new job because I moved and I'm not sure how to talk to my boss about it. Before moving I was in a small town that I grew up in and everyone knew everything about everyone so I never was accused of making up an excuse or anything. I want her to understand what I'm dealing with when I get a migraine and I don't want her to think it's just an excuse. I also don't want any of my co-workers to think the same. Just curious how y'all would go about talking to your boss about something like this. PLEASE HELP!!