He may not understand the severity of the phobia, everyone has fears and things that make them uncomfortable, he may not realize this is something that is a real issue for you and not some fun cute little "Eeek I'm afraid of spiders" phobia. I think to someone who can't relate, it would seem a bit odd, so maybe describing specifically how you feel and what the anxiety feels like would help. I would hope as your boyfriend he would want to try to comfort you in times of illness and not make you anxious, but if what you really want is him to get as far away as possible when you feel like vomiting, tell him that, and explain in great detail why to get your point across.
By the way you talk about this guy in your post, it sounds like not caring about you is a problem in general, and maybe you should address that problem with him, and tell him you don't feel like he's paying attention to your feelings and being considerate of them. Maybe he doesn't realize how he's making you feel. It's definitely not ok for him to make you feel that way.