Dealing with weight gain as a new grad on nights?

I use to be fairly active before I started on nights as a new grad in ortho. Dealing with all the stress as a new nurse and suffering the effects of working through the night (and sleeping through the day) has slowly begun to have a detrimental effect to my health (specifically my weight-I've gained about 5 lbs the last month). Whenever I get off work, I'm too tired to go to the gym and I just indulge myself into some comfort food (shame on me....). I know the first year is going to be tough, but do any of you have any tips? I use to go to the gym 6x a week, but am only able to go at most 4x a week. I

Thanks.