I played competitive football also and we had a number of guys on the team who would vomit prior to each game and it was well understood that it was nerves... i would tend to believe it is the same with your heaves.. you may outwardly be dealing with the anticipation of the game but inside you may not be coping so well and may not even know it.. if it were occuring through out the day i would think otherwise...not a doctor but i dont think there is anything to worry about..
Hello,
This sounds to me like you should see a sports medicine doctor. I am not am doctor... but I think you should start there. Also, don't get mad... this is not an insult, I am just trying to help you... Since your problem happens before sports only, then it may also be something with your nerves/stress. I sometimes get this feeling before cross country meets when I am very nervous. If your problem is similar to mine, you can help it by drinking water, relax, and take deep breaths. Hope some of this helps!