During my longer fasts I’ve experienced similar sensations… The cramps weren’t worse than menstrual cramps, so I just kind of endured it and they eventually stopped. The burning feeling was weird, kind of started in my stomach and then I felt it travel slowly down my intestinal area, twisting and turning, and when it reached the end it stopped. It wasn’t overly uncomfortable, more of a curious feeling, so I let it pass. In these situations I tell myself “This is what losing weight (or perhaps autophagy) feels like.” Hopefully that type of thought is not too problematic! In my case, the pains were not unbearable or excessively painful, but if it got that bad, it’s probably time to end the fast.