Do you generally get the nausea after eating heavy or especially fatty foods? My bf was having this for years, and recently found out it is because of his gall bladder. Particularly high fat and/or cholesterol foods are hard for him to digest, and the condition will gradually worsen over the years. He is going to have his gall bladder removed in the spring
Another reason could be simply that you are consuming too much. Even if you are bulking, you may not have a high enough metabolism to support a high caloric intake, in spite of your body weight. I'm not qualified to give training advice, but perhaps some cardio will help balance out your caloric receptivity
And the other possibility, which you probably know, is size and frequency of meals. If you're hungry for a while before a big meal, your stomach is going to be strained