I wouldn't say you have to start OVER... overall what you ate wasn't that bad. Just make the next day better! Keep improving. And it would be good if you stopped using the microwave. It really isn't that difficult to heat water on the stove, or heat your food on the stove or in the oven. Really.
Could you get a bigger bottle for your water, so that you could just bring one large bottle from home? Water from the tap isn't very good. But if you are in a pinch, water from the tap is still better than, say, iced tea or Coke (all those bottled drinks are made with tap water anyway).