I know this is really tough for you - ask yourself why you should feel guilty about this. You aren't responsible for her moods; guaranteed she's not going to be happy when you tell her! But her moods are hers to own. And you're certainly not to blame for her IBS. I know that it's easy to feel like you're making it worse, but she needs to own her problems the same way you are trying to own yours. Chin up, and don't be afraid to take charge of your life!