Am I overtrained, and what to do?

Rest is the cure for overtraining.

As to whether you are overtrained or not, without more information its imposible to tell.  You may just have had a bad day when you did your 3 miles.

Without seeing anything in your logs it's hard to say.  I wouldn't necessarily say you are overtrained, but you might be overworking yourself.   Your workouts the past few days seem to be at a high level, where you are continuously pushing yourself.  Do you always work out at your limits, or did you first work on building a good base when you started your training in April?

Just because you have a slower run does not mean you are "overtrained."

Overtraining is denoted by fatigue, inability to elevate your heart rate, and slow recovery, none of which you are describing.

There can be any number of factors that cause a slower run.  Time of day, weather, what you ate for breakfast/lunch/dinner, your workout the day before, etc.

Next week I would recommend devoting one day to each discipline doing low intensity short workouts mixed with a few strides for running, sign sprints for cycling, and 25 yard sprints in the pool.  Not enough to cause fatigue, but enough to "excite" the fast twitch muscle fibers adn get them ready.  Then two complete days of rest before the race.

But that's just me .......

Morning resting heart rate is a way to tell.  You need to have  a base line though.  If you are overtraining you may see that rise.  The body is working hard to repair the damage done by overtraining. 

Personally when i got a little crazy mine went from 42bpm to 55pbm.  I felt slightly depressed.  Look through the article there is some stuff on it.

Have at it,