How did I get here?

People who are not overweight dont understand what it feels like to carry so much weight. Just imagine if you weigh about 150 pounds (68kg) and you were made to carry another human being who weighs as much as you.  I am 6foot 4inches and I have been told that my ideal weight should be around 215-220pounds (97-99kg) but at the moment I weigh about 360pounds (163kg).  I am 140pounds overweight. Being overweight is not cool at all.  I mean the simple chores of life like cleaning, walking to the bus stop or walking up the steps seem so difficult.  Even getting out of bed most times is so hard.  When you are traveling by plane, you cant just sit anywhere or sit beside just anybody.  You occupy so much space and this can be very embarassing.
It makes you so lazy. I know I have to clean my apartment but I just cant bend down like a normal size person and get the job done.  Sometimes I dont clean because it hurts my back or knees when I have so much movement. 
And it really makes you loose your self confidence.  You dont want to take your shirt off infront of other people because of the way your body looks.  You only wear certain kinds of clothes.  You cant just go shopping at the regular clothing stores.  And offcourse there is the constant stares from people. And the sex is not fun for us fat guys I can tell you.  I mean I love sex like the next guy but the energy is not there most times.   
I was never this over weight.  I keep asking myself how I just let my self go like this.  I look back and try to figure out what happened?
At age 22, I was in very good shape.  I was very active and I was even thinking about becoming a personal trainer at ballys fitness club.  I mean I trained 4 or even 5 times a week. I watched my diet and stayed very active.  I played basketball regularly and even joined a semi pro football team.  So seeing  myself this way today really baffles me.