Hold the phones is this a breakthrough!????

Since the pull buoy is used to elevate your legs when you are not kicking, I would look in this area as being your problem.

I'm guessing it puts you in a flatter position in the water and more efficient.  You may also be right about kicking too hard.

Focus on the 'flat' feeling in the water the buoy gives you and try to mimic that without it.

The pull buoy supports your legs, which appear to sink when you don't use it.  It shouldn't be used as a substitute for a poor technique, rather it's a tool to be used in certain sets.   The lessons will definitely help with that

If kicking is your problem, ditch the buoy and get a kick board.  Or just do kick drills without the board.  Either way, it sounds like you need to do kick drills to get your lower half moving correctly, then you can piece it together.

When your head it too high in the water, it drops the legs.  A pull buoy will negate this effect, which is not terribly helpful on race day.

What kind of drills do I do with a kickboard? Last nights swim I noticed that when I put my head straight down I can get the groove better. But looking at a smooth swim website it says that I should tilt my head up a little? When I do that I have to kick my legs harder to stay afloat or I have to swim faster. Is swimming like running were you have to build up before you can go further faster?

I have to disagree with this.  True, you don't use your legs like a sprinter in the water, but a strong and effecient kick makes you a better swimmer.  A better swimmer uses up less energy because they either finish faster or can move at more relaxed pace.  Using less energy in the water makes you a better biker and runner on race day.  A good kick makes you a better triathlete.

To be honest, I have no idea where I put my head or what angle it's at when I swim.  I just swim what's comfortable.  There's a whole lot more than looking down or slightly up that can screw up a stroke worse.

On the board, just hold it out front and kick for starters.  Getting some fins will help build some strength.  Kick on your front, kick on your back, kick on your side, do the fly kick, etc.  All will help you build a stronger, steady, efficient kick, and doing them without the board on occasion can help you find a streamlined position and help out with that sinking leg feeling (and not mask it with the buoy, which does serve a purpose, but that purpose should not be a crutch to hold up the legs).

And yeah, swimming is sort of like running in that you have to build up.  Now, when things click, it's nothing for people to go from swimming 400 yards in a work out to 1500.  It'll take some fitness gains to get to say a 3000 yard work out, and it'll take a heck of a lot of training and building to get to 3 mile work outs.  I know it seems far off, but anyone can do it if they put in the time in the water.  Check out the beginner and intermediate swimming programs on this site and get in the water

Here they are:  LINK

The beginner's program starts at 700 and works up from there.  Good luck and have fun!