Time ... where is the time???

OK, I have nursing school classes, studying, Reserves, work, volunteer hours, house cleaning & wife duties to attend to ... WHEN exactly am I supposed to fit in workout time? The days I could probably squeeze it in I am too exhausted to go. I have basically done nothing. I still haven't signed up for the YMCA and I am so not dieting. I did replace my usual junk food with the "100 calorie" alternative. UGH!