I have various days when I feel either slimmer, fat, ugly, possibly looking good etc. I think it is the way that the mind works. This summer I had knocked dieting on the head and was forever eating out, be it Wagamama's or MacDonalds, local chip shop etc and I never even thought about my appearance because I was in a couldn't care less mode. I think we are now very conscious of how we appear physically and sometimes over critical.
Jim, you are definitely moving in the right direction as you are losing weight - ignore any negative thoughts.