Well,i have experienced from this kind of incident before. I think its because u drink plenty of water after your meal.Oil as u know will float on water suface.Thus,causing u to spat up oil residue that u eat.
I doubt if it is oil. It's more than likely bile and stomach acids. Women are more prone to gallbladder attacks like this especially if you are pregnant or have been pregnant. Get your gallbladder checked. It could be stones or the pre-stone formation. It made me sick as a dog too especially when eating fatty foods.