Feeling like I'll never be able to live my life - gained everything back in only a month

I worked so hard for a year to get to a body I was happy with, by being so careful about what I ate all the time. It felt worth it because I felt so good about myself. I'm 5'0 and got down from 135lb to 110.

However, this summer I got a job that was sort of a dream job. It was 5 weeks and it involved a lot of physical labor, and also I did not have the ability to cook my own meals, I had to eat communally. I thought it'd be okay because I was on my feet doing hard work all day. I generally tried to skip carbs, have half-dessert on days it was offered (once or twice a week), and not snack. However, I got back and none of my clothes fit. Even the clothes from before I started losing weight don't fit! I haven't weighed myself, but I think I must be heavier than when I started. That's 20lbs in 5 weeks!

I feel awful, and I feel hopeless. What's the point it being so so careful if 5 weeks of STILL being more careful than everyone around me gets me back to where I started and then some?

Have any of you had an experience like this? What can I do?