I've done that.

I gain weight so quickly it's not even funny. And when my husband (then boyfriend) moved in I gained about 100lbs over 2 .5 years and kept it there for another 2.
Don't beat yourself up over it (I'm one to talk, but I know it doesn't help). And, now that you've gotten to the point where you know you have to do something, it's time to do it! And you can. Do you have a specific eating plan you'll be following?