I do not have your problem and am happily sexual, but I am aware of a general approach to all problems of this type. The approach may seem paradoxical. Basically you gradually expose yourself until you become desensitized. I highly recommend this approach because you would otherwise keep running into this problem.

If you want to vomit, it is OK. You are not going to die from vomiting. If you really want to vomit (rather than using this expression as a figure of speech), go to the bathroom and vomit. You might feel relief and even something cathartic from it.