We are often told that this health and fitness journey is a marathon not a sprint and as cliché as that sounds I think it is important to remember that most marathon runners talk about "hitting the wall" and it is the time when they just have to push through. This sounds like one of those times for you. The problem with so much of what you are describing is that all these emotions and behaviors feed off each other. Stress causes lack of sleep and mindless eating; lack of sleep increases stress and mindless eating; mindless eating leads to weight gain and weight gain causes us to put more pressure on ourselves and it starts all over.
This journey is 100% between the ears and I find if I am going to be successful and resist temptation I have to set my mind ahead of time and then I have to keep it set. If you know someone is going to have treats to offer you at work, bring some healthy snacks with you so you have a choice. While they are eating the sugary snack, you can have your healthy one. Keep a water bottle with you at work because water does keep you full and gives you energy (even if you are sleep deprived). If you are able to get away for a few minutes while at work, take a short walk outside to clear your head and release the stress.
It's hard to focus when you have so much going on so why not take some time in the morning and at night to journal your feelings and like ARCHIMEDESII said "accentuate the positive" and plan for ways to avoid the negatives.
And whatever you do, leave your work at work! We work to live not live to work and you cannot allow the stresses of your job to impact the progress you have already made.
Stay strong and congratulate yourself for recognizing that you needed encouragement and support.