What does it mean if I feel like throwing up after sex?

An unusual response. Questions you might ask yourself: is sex enjoyable and you still feel nauseated afterwards? Do you have any gyn problems? Are you currently pregnant? Are you asked to do things that may be unpleasant for you but you do them anyway? What is your relationship like? Are you afraind of getting pregnant? Talk to your physician and try to think about some of those questions before going.
Headache? Could be any of a number of psychosocial problems as per dr. Hazlett. Also consider post-coital headache secondary to orgasm - that is if there is a headache. Rarely, migraine equivalent can occur where there are the associated symptom but no headache. If you experience vomiting, blurry vision, change in pupil size, or stiff neck, it may be a medical emergency.