When I did WIWO with Alex, we did really well and I cracked it after about 1 month..............................or so I thought................. all of a sudden she started performing again, and this time with a vengeance, so be aware that you might have a regression. This will usually happen after they fall asleep independantly and sleep through the night for about a week on the trot and you think it is safe to open that bottle of wine that you have been saving to celebrate the occasion and then................ wham, they have nightwakings, early waking etc. My advice is, don't open the wine, and contine to walk in walk out!!!
Don't be disheartened by this, they just have to test our stamina once in a while!
Kathrynk's suggestion abot food is spot on IMO. Food is so important, we do dinner around 5ish and then supper at bedtime. This can be anything from a bowl of cereal, yoghurt, toast. Jst a snack to keep going. Worth a try
hth