swim help needed

Breathing out under water - try both and see which feels more comfortable.  I have heard two arguments (1) breathe gently out of your mouth to release the bubbles in a continuous stream between breaths - and this is in fact the way I was taught 30 years ago! (2) keep air in and breathe it all out just before you take next breath.  I actually prefer the second for me, despite being able to do both - and apparently it helps with your buoyancy as air in the lungs keeps you more buoyant.

 As for kicking - practice practice practice.  A lot of people don't use their legs too much in the actual triathlon but when learning to swim properly it is essential to be able to do this.  It is kick from your hips NOT your knees - the amount is dependent on comfort again.  You will only go backwards if you are not pointing your toes.  Two things can help with this (1) try swim fins - and this also helps to keep your kick going more easily whilst you work on arms/ breathing (2) at home kneel on the floor on your feet - helps with  foot flexibility.

 Good luck - whilst I can always remember being able to swim, I have seen so many posts about breakthroughs whilst learning, it is inspiring. I look forward to reading about yours too.

My first piece of advice is to get some lessons as soon as possible.

As for breathing.  When my face is in the water, I'm exhaling.  When my face is out of the water, I'm inhaling.  That's about as complicated as it gets.

The kick in triathlon swimming is for balance and maintaining a good body line.  If I had to guess, you're proabably furiously kicking with a bunch of knee bend, but still feeling like you're sinking, thus kicking even more.  This burns up the oxygen and is why you can't go more than one length.  There are drills and stuff you can do, like a kickboard, but get a lesson as soon as you can.  

Steady, controlled, exhale while your face is in the water.  I tell people to hum which forces air out through the nose (keeping water from entering the nose).  Roll to the side for a quick (controlled) inhale, and your back to exhaling. 

For the kick.  Start with your hips (really core rotation) with your knees and ankles loose.  If you sit on the side of the pool with your feet in the water, kick them (together) back and forth with your ankles loose.  You'll notice your toes point away when water pushes on the top of your foot, and they hook a little when pushing your soles against the water.  Your knee is the same (but harder to demonstrate). 

Practice, practice, practice!

I started swimming in May on my own.  Was out of breath in 25 yards.  Worked on my own, fought the water and was able to swim 300 for a race.  Joined a masters swim group and the coach worked with me one on one.  She had me stop swimming entirely for about 2 weeks.  It was drills, drills, drills.  Now, I am swimming the entire masters workout (2850 yards this a.m.) and could do the entire distance without stopping if I had to.

I struggled with the whole breathing thing too, I was gasping for air.  With time, your in-water aerobic capacity will improve and it will get easier.  Plus, I find my swimming improves every single time I get into the water.  In fact, I swim better mid-workout than I do at the beginning. 

Kick from the waist and don't kick too much - the harder I kick, the more tired I get! 

A coach will really help you and I really recommend it.  Good luck!