New to Everything

Hello, I am from CT and brand new to all this. I am 29 years old and I have never done any sports in my entire life. I have always been okay in terms of weight (actually under weight for a very long time and then became a bit overweight after marriage) most of my life, until a few months ago I saw a photograph of myself with my gut hanging out. I got very disgusted with that, and decided to get back in shape - this time in a healthy way instead of pure starvation. So I started going back to the gym, got a personal trainer and started working out.

About a month ago, I saw that my gym was holding a mini sprint Triathlon (10 min swim, 30 min bike, 20 min. run) at the gym. I had always wondered if it was ever going to be possible for me to do a triathlon. (My brother-in-law started doing triathlons a couple of years and even did an IM last year. We were his cheering squad. ) Anyways, inspired by my new found love for working out and my brother-in-law, I decided to give it a shot.

As I stand right now, I basically suck at everything. I can't swim for more than 6 minutes at a time, can barely last on the stationary bike, although I have gotten to a point of finally being able to run for a full 20 minutes (very slow pace, but can run, somewhat).

I am still determined to do the sprint in January and if I survive it, may be a longer sprint in May. Any advice I can get from anyone on how to better myself, will be greatly appreciated.