When I started on my weight loss journey I was about your size. For the longest time I didn't really exercise AT ALL, other than walking to and from places nearby in my own pace. I didn't have the strength to do anything more than that.
However, a good weight loss plan helped me to lose enough kgs that I was able to start doing more, and it became pretty obvious to what extend I could do it. I am sure it'll be the same for you.
Of course, I'm not saying that you should NOT exercise already - I'm just saying that the dieting is a more important factor to lose weight. The exercise is a great addition, but if you can't do much then just do what you can.
Enjoy your weight loss journey - make sure it's a good, positive experience - that's when it becomes easier to reach your goals.
"Keep your friends close, your enemies closer, and the cookies at the other end of the table."
"Eating less, moving more, not eating stupid s**t = losing weight."
"Do. Or do not. There is no trying."
- Master Yoda.
I started my weight loss journey on October 4th, 2010 - and this is what I have accomplished so far: