I would punch you in the arm if you were sitting next to me right now!!
Being overweight doesn't mean you don't have exercises that you prefer and that you are best at. Lots of people can't get in the water, or swim 1 lap, and you can. That's a "strength", and you have lots of them, whether you acknowledge them or not *arm punch!*
One buddy to another: I think you should do that November tri specifically. It's 3 months away which is the perfect amount of time to get meaningful and safe gains. If you say you will do the tri if
you lose weight, then that puts losing weight in the balance as the variable that determines whether or not you do the tri. You may not lose weight because the tri "deadline" is flexible, then have neither in November. Making a concrete goal, like "I am doing the triathlon at my gym on November ___, 2012. My plan is to swim, cycle, and walk 1x per week each for the next 3 months, and my goal is to need a new bathing suit due to weight loss by November." will nail down your mission and help you stick to your plan, because there's an end in sight. If you feel strong enough to take this on now and are motivated, I say put it on your calendar and train for it girl, you can do it! I know you can. Don't be scared. You can do this and you can do it really well. If you just believe in yourself every day between now and November, everything you want to do will happen.
....I know you might say, "Thanks for the advice Karrie, but I'm going to see how it goes."
That's okay too. You know I'm excitable and I like to make goals. Have a great Sunday babe!