Welcome to the forum. My answer would be somwhat similar to the others. You should tell your immediate supervisor, but make it clear that you are working closely with your doctor to get a good treatment plan established. Hopefully they will be understanding, and look at migraines as the disease that they are and not just "bad headaches".
As for working, it takes some time to adjust. I know personally I've been through several different medications and doses before I found something that works. So try not to get frustrated (it only makes it worse!), and make sure to keep in touch with your doctor on what is working/what isn't. Keeping a headache diary can help too so that you can identify your personal triggers.
Some things that I do to manage working day-to-day...I go for walks during breaks at work to help reduce stress, that really helps. I keep a britta filter in my office so that I have no excuse to not stay hydrated. I keep a heating pad and an ice pack, which can help avoid a full-blown headache if I get a neck ache or sinus pressure. And of course I keep some of my triptan medication with me, and take it as soon as I know that it's coming despite all this (and try and put my head down for 15-20 minutes). Also, because mine can be triggered by stress like ckt said, I have learned how to use deep breathing and other relaxation techniques to get through those times before I let myself get all worked up.
I hope that things start looking up soon!