I do have to agree with everyone else that it's best that it happened now and not when you are married and have kids. I understand what you are going through (though, not quite as badly); I was seriously dating a guy and when found out I was getting an ostomy he told me he could no longer be with me! Ridiculous!
It is absolutely not your fault and you are not to blame. He's the one at fault. Clearly, he is a coward; you're the brave one! You didn't choose to have this disease and you can't choose to opt out if you want (we all would!). But he obviously had the choice and chose the lesser course...he truly is a coward. He WILL eventually see his mistake and see everything he lost in you.
But I think the BIG question here is, is there some *** whooping needed here? NEVER MESS WITH CROHNIES! Just say the word and we'll all be there and give him a piece of our mind! Then we can have a HW party at the local restaraunt! :0)
But seriously, big hugs to you and let us know if you need anything!