I get a post ride headache/migraine every time I ride. It usually starts out with a small spot of blurry vision that gradually grows larger and larger, then eventually goes away after about an hour. This is usually followed by a headache about 20 minutes later. I have had it happen during the second half of my ride or on the drive home. What little research that I have done has told me I could just take some type of pain killer to resolve the issue but due to a pre-existing condition I am limited to what medicines I can take. Does anybody have any suggestions as to what may be triggering these headaches. Thanks