I have been there...oh heck yes. So let me tell you that you absolutely can get right back to feeling good, Harlekini! When I first dropped all the bad stuff -- esp grains and sugar -- I felt great, yet still often slipped up and fell off the wagon. When depressive symptoms strike in addition to feeling physically lousy, it's so terribly demoralizing -- believe me, I know! I have been there over and over.
You're still early in the process -- expect yourself to cheat. It's gonna happen! With time, though, cheats naturally come fewer and further between. The less you beat on yourself for it, the better. As Mark Sisson says, "Don't let the perfect be the enemy of the good." (Easier said than done, I know.)
The body is a marvelous machine; it can heal up from the worst excesses. I would bet my front teeth that your stomach isn't wrecked, it's just feeling a bit crappy. Depressed thinking will make it seem like it will never get better, but it will.
The fact that you're not having carb cravings is a very good sign. That should make it easier to realign your diet and kick all that junk right back out of your system. And the fact that you felt GREAT before the junk food kick means you did not ruin your stomach -- it's just sensitive.
Remember that you're not alone; there's a huge community here of awesome folks who are willing to help out. We all struggle too...I don't know many people who can say giving up cake was a cakewalk. ;)
Be well, and don't give up!