That really sucks, I would mostly agree with Rosco, your body is rejecting the toxins and is telling you in the best way it can, is there any throwing up? usually nausea is a way for the body to get rid of the build up of toxins.
doctors can't do anything about your cannabis smoking, if you keep getting this, take some laxatives, and drink a lot of water or v8 juice this will help you with maintaining a more healthy body while also helping the sickness & toxins trapped in your body.
just a suggestion, hope everything goes well.