it's totally cause of the tobacco , smoking the tabacco dosent hurt u , but holding it in for a moment , since u do since ur smokin weed too , tobacco makes u feel nautious if u hold it in cause its not meant to be smoked like that , its post be in hales and exhaled as soon as u take a drag , if i were u id lay off the ciga-weed and jsut stick to a normal joint then the tobacco afterwards if u really wanan get rid of that nautious feeling