Glad to hear you're not taking all of the medications at once. I agree with everyone else's posts as well. Get the imitrex, it may work even in the middle of a headache. Get rid of the Excedrin. Caffeine is a bad trigger for me, sometimes it works in the short terms but I always pay in the long term.
Something we use a lot in Canada for nausea is called Gravol. It stops nausea and makes you sleep. On a recent trip to the states I found it under the name Dramamine (sorry if it's spelled wrong). I've never used phenergan, so I'm not sure if it's the same.
Have you tried some non medication alternatives? Relaxation, massage, warm bath?
If once you've tried the Imitrex it doesn't work, I would make an appointment with the doctor and go and see him / her.
The secret of health for both mind and body is not to mourn for the past, not to worry about the future, or not to anticipate troubles, but to live in the present moment wisely and earnestly. Buddha