Being that I'm postmenapausal myself. I had a TVH at the age of 27. I've also suffered from migraines for 10yrs.......... I can relate. I've been on Imitrex but it didn't put a dent in my Migraines. Neither did Inderil. The Imitrex injections help me sometimes. If not, I'm off to the ER. I am now on Topomax. I have been through them ALL!!
Amerge is somewhat like Sumatriptan. Which is in the Imitrex family. So, if I were to venture a guess. ..if the Imitrex is not working as well for you, this may not as well either. If it were me, I'd give it a try. Anything is worth a try. If it does not work then you can ask for something in another family group.
My migraines did the same thing you are speaking of. They changed in frequency and duration as well. It got to the point to where I was having 3-4 a week. I told them they HAD to do something. I could NOT function.
There is also Depakote. I myself can not take it. I wound up having an allergic reaction to it. Please DON'T let this deter you though. They always seem to forget, I'm not 5'6" and 160. It overdosed my system. I also tried the Botox, which is now being used for Migraines. Well, that also caused a reaction as well. You have to just keep trying something that works with your body. When you do, stick to it. If your migraines change again, let them know. Don't suffer. I hope this helps.