I know how you feel!
I started at 300 in March 2011 (after gaining back what I'd lost in 2008), got down below 250... then things in my life went out of control and so did my eating habits and I got back up past 300, all the way to 330. I recommitted to getting healthy in May of this year, and have stuck with it through some seriously stressful times and am back down almost 50 pounds!
It can be done! Good luck to you and knowing you need to make a change is a big step in the right direction so welcome back!