Please don't be so hard on yourself. I've been doing SW for quite some time and have seen many ups and downs with my fellow SWers as well as myself. I can tell you now that it's perfectly normal to put on 6-10 pounds on holiday and the same at Christmas. We all do it - so you're normal, not a weakling or a failure - you have nothing to be disgusted about at all! Add on a good few pounds for TOTM and that accounts for all of your gain. But please don't lose heart.
What separates the winners and the losers in SW is that the winners take it on the chin and think well I enjoyed that but it's back on plan I go now and I'll soon shift that extra weight. This is the right attitude especially as most of it is temporary bloat anyway and comes off much easier than the first time around - easy on easy off is a mantra I find particularly useful as it's borne out to be so true. The losers think oh I'm such a failure I may as well go and eat a hundredweight of mars bars to make myself feel better. And does it make you feel better? As someone who's done it herself I know it doesn't!
So chin up sweetheart, welcome to the real world where holidays and Christmases and birthdays happen and get in the way of dieting. We ALL gain during these times but that doesn't make you a failure - just HUMAN lol! Wishing you all the very best and let us know how you get on, hugs x