Why do I wake up feeling disgusted or remorseful?

For the past few weeks, I've woken up and felt this aweful feeling in the pit of my stomach, and it just feels like I'm disgusted or ashamed for doing something terrible, like I've done something wrong. But I haven't done anything that I regret or feel bad about. I just feel like **** and a scummy person, and I don't understand why I feel this way. Please, has anyone else felt like this, or has any idea why its happening to me?

I have GAD and have been on antidepressants (lexapro) for the past month, if that helps.