I've had migraines since I was 17 and I'm now 38 and alcohol has always been a trigger for me. In my teens and twenties I drank alcohol regardless and would usually wake up with a migraine the next day which I wrongly labelled as a hangover! I used to wonder why my hangovers were so much worse than my friends, now I realise that the day long headache/vomiting/intense pain on the left side of my head was actually alcohol induced migraine.
As I've got older I've been able to tolerate alcohol less and less, for a while I could drink small amounts of clear spirits i.e vodka and be reasonably ok...but if I drunk wine I would be ill for days. Now though I can't tolerate any alcohol at all. The last time I drank was last year at a family event and I had to go home early the small amount of alcohol I drank triggered a migraine within 30 mins that was so bad I was in bed for the next 2 days! Not worth it, so now I'm teetotal
I read somewhere about alcohol containing high amounts of tannin which can cause migraine in some people, red wine is especially high in this which explains why many people get a headache after drinking it I guess :)
As for the migraines changing pattern, mine have gradually got worse as I've got older and I seem to be much more sensitive to any triggers now, sometimes I can have a few months where they seem better then bam I get a month of sheer hell although I did absolutely nothing differently!
Hope this helps :)