Nausea, diarrhoea and abdominal bloating are quiet unlikely to be associated with pregnancy, it rather likely to be associated with some GI problem. You have not mentioned the duration so again diagnosis becomes difficult which could vary from some infection, to some protein allergy, to simple gastritis. I would recommend you to be on simple liquid or semi solid diet with some pro biotic drink or capsule and lots of fluids to replenish the dehydration. if symptoms persist please see your physician