I was always naturally very skinny when I was younger, but from about 2005 onwards, I put on a lot of weight. I couldn't tell you how much I weighed, but my waist size was just over 34" (which is very large for a small-framed guy of 5'4"). I decided to go on a strict diet in 2010 and cut out all the crap food.
These days I'm very healthy, and I feel absolutely amazing. I love running, walking, rowing...anything that keeps me in shape really. I'm very precise about my diet, too.
It's not easy to stay focused in the early stages, but you already have the right mindset and sound very committed. You can do it!
If you need any tips or advice, just shout.