I get awful neck and head pain after sex about 7 times out of 10, its ruining it for me, me and my girlfriend have gone from sex at least every other day to about twice a week, its baaaad.
I mentioned it to my GP and shes put me in for a MRI scan to check for brain damage. She said it could also be due to the large amount of stress your body goes through during sex that causes it, altohugh it never happens when i go running etc.
Could be a related thing, as obviously intense arguments put a fair bit of stress on your body. Co-codamol from Tesco works well