Thank you for your query.
Your boy friend's vomiting
has nothing to with the use of condom. You need to sit down with him and try to find out what disturbs him and he vomits. He needs to understand himself and his body as vomiting has nothing to do with the sexual act. If need be counselling
may have to be sought.
I hope I have responded to your query to your satisfaction.
Wishing you both all the best.