a bad day - BLS

I have had a bad day today, my weight watchers hasnt gone to well up till now either!
well anyway today, i went to basic life support today and ended up in tears.
I was just too fat to get into the correct postion to hold the nose and blow into the dummies mouth, I had to get right down onto my elbows to do it. The nurse came over and saw I wasnt doing it right and basically said to me well you need to demonstrate to me you can do this, if you cantdo this then you cant pass...in other words I wont progress on the course!
so I found a way round my dilema hence right donw on my elbows, this is while the nurse looked on at me with a pitying look and I just wanted the room to swallow me up. So I then go in for the test to prove I can do this, and well thankfully I pass and she says well done, then has a chat with me about my weight. At which point I start to cry my eyes out and leave the room in tears where all my fellow nursing students are asking what is wrong. I drove home and went stright to the gym and signed up!
I feel so ashamed I am this size, and so fed up with being this size, the journey ahead just seems too big. I wish I knew why I dont take my health seriously..... I know im over weight, I know I am putting my life at risk, I know I would be happier slimmer, I know I would feel happier going to the gym, I know my kids want me to lose weight ....so why dont I do this? why does it never succeed? why do I not care about myself as much as I care about others?