I do think that estrogen has something to do with migraines, usually when you alter your estrogen level up or down. Is there a way you can cut the patch in half, or cut your dose in half somehow? I was on Activella tablets and I had trouble with migraines, so I started skipping one tablet per week, then two tablets per week, then I took one every other day. The migraines stopped. I also had high blood pressure, which I didn't realize, so I got some medicine for that, and now I rarely get a headache at all. I'd say that if your migraine pattern is different now than before, the only thing that has changed is that now you are on HRT, so maybe you should try to see what the lowest dosage is that you can use and still feel okay. Also, if you don't know what your blood pressure is these days, check that, too, because at meno there is a tendency to develop high blood pressure, which causes migraines (at least it did for me). Let us know how you are doing.
I switched to Vivelle Dot patch last year for a brief time. I experienced terrible migranes, usually within several hours of applying a new patch. I had to switch back to Climara and the headaches disappeared. Hope this helps.