Weight shock, skinny to fat, fml

I've been steadily gaining 10 lbs a year the last five years. Used to be skinny, now at 170 I'm feeling quite overwhelmed. I used to be able to just cut back on foods and 5 lbs would magically melt off, now I need to exercise too. I don't hate exercise, but it just takes a lot of time, shower time, more laundry and I'm a busy student. I try to get jobs where I'm on my feet and busy, but it seems to just keep going up. I know how to lose weight, just need to motivation. In an effort to motivate me my fiance (who has watched me expand for five years) just tore me a new one today and pretty much told me he's not attracted to me anymore, that I should try to look nice and he's cried because I used to be so thin. Not so motivating, just depressing. So now I'm on this site to understand the numbers better with calories in and calories burned. Kinda just want to roll away with my fat self and get skinny for the next lucky man.