First, take a deep breath. Don't forget to let it out!
This whole process can be overwhelming. I weighed 295 when I started, so I know where you're coming from.
I agree with both of the posters above in terms of what to do... but that may still be overwhelming.
I took baby steps. When I started, about a year ago, I just watched portions. For example, I remember a particular meal at a place like Bob Evans. I used to get the eggs with bacon, hashbrowns and pancakes. That day, I decided to just get eggs and toast. I wasn't stuffed when I left, but I wasn't hungry either. I told myself that feeling was okay and that I could always have something to eat later if I wanted to.
I also tried to move a little more. Not exercise, per se, but getting up and moving rather than shouting for something. Eat less, move more was the plan.
The process of portion control did require me to pay attention to what I was eating, but I wasn't really sure what I was doing. After about a month, I started journalling everything I ate and calorie counting. Then I started paying much more attention to nutrition.
I also started to exercise. Not much at first, but some. I have found a way to make myself accountable by setting exercise goals each month (in terms of number of minutes!)
So, take some more breaths and come up with a plan. Try it out. Come here and learn and read and be inspired.
You may want to check out the 300+ group or the 100 pound club -- you'll find both under support forums.
You can do this, you know. You don't have to believe that now, but take a leap of faith and start!
My 5 C's of healthy living: Commitment to conscious control, with the understanding that choices have consequences