I'm sorry to hear this, GGB. I would imagine it is very frustrating for you to get her (and you) worked up and then have her shut it down and refuse to continue. It's pretty crappy. Have you talked to her about this, how you feel when this happens?
This may be a "duh" question, but if you go to IC, does it seem that she's not that into it and so it's not as enjoyable for you? That she seems more "willing" than "desirous?" Is that why you continue to pursue oral, because if you go directly to IC it feels like you're "settling?" During IC she doesn't get as aroused, so she doesn't feel panicky and she allows it to continue to the end? Does she start out being interested in oral? Or has she expressed a preference for IC instead because it's less "scary?"
I have my own panicky feelings that I think I'll elaborate on in my thread. It will answer some of Cobra's questions that I never answered last week.