I suffered debilitating migraines until week 16 - I am talking 6 days out of 7, spending most of my time in bed in awful pain. I went to a specialist and here is some of the advice she gave me:
Firstly, make sure you eat, even if you then vomit it up, some of it may stay down. Eating can really help. You are allowed take motillium when pregnant - I find it useful to take it immediately after I have vomited, then it has some chance of working, if I keep it down then I take painkillers around 15 minutes later. Cold compress at back of neck/on forehead can help a small bit. Cold shower may help a small bit. If you can do yoga on the days where you don't have a migraine that will help, as will meditation.
Migraines can be caused by lots of little triggers piling up and finally reaching a threshold that causes the migraine - these include food triggers (caffeine, chocolate, citrus fruit and cheese in particular so try avoiding all of those things), lack of sleep (so try going to bed an hour early on days when no migraine and you won't be in bed anyway!), stress (so try and be easy on yourself - I was stressing so much about missing work when I had all the migraines and it really really didn't help. If you have a migraine you can't do anything and it's not your fault so you just have to be kind to yourself about it.), being at a computer screen too long (so take at least a 5 minute break every 30 minutes - I was advised a 10 minute break every 30 minutes). and then obviously hormones, which when we are pregnant we can't do anything about.
Unfortunately nothing I did really helped and I just had to suffer for weeks and weeks BUT it stopped at week 16. Not entirely but more or less. I have had a couple since then but not every day like before. i still am having loads of headaches but applying all the above tips really helps - but not overnight, it takes time to apply these new habits.
Remember to eat - if you leave crackers or something by the bed - when you wake up with a headache or migraine, eat one immediately. even if you vomit it up later.
And obviously, drink loads of water, ditto even if you have to vomit it, just keep drinking.
Hope this helps and so sorry you have to suffer this. It is so awful.