Many people get aroused or even orgasm during rape. Its just the bbodes natural response to sexual stimulation. It doesn't mean he wanted it or that he was willing or that hes happy about it. You should have more respect for peoples boundaries. Codoms protect you from pregnancy and you both from diseases. It would be wise to start using them at least until your on the pill and you both have been tested.
You should also apologize to him and ask him did you cross a line?
"Don't ask a question if you can't handle the answer".