I highly agree with the strength training responses.

You also mention that you run 8k every morning and do burpees afterward. I think you should read [this post](http://www.marksdailyapple.com/case-against-cardio/) by [Mark Sisson](http://marksdailyapple.com) about why doing too much cardio could actually be **bad** for you.

One other extremely important thing is your diet. I know you mentioned that you eat well, but recently, I've discovered that the typical person's perception of "eating well" may not actually be as healthy as he or she thinks it is. In particular, you might be consuming too many carbs to fuel your cardio. See [this thread](http://fitness.stackexchange.com/questions/4609/what-books-sites-journals-and-research-can-you-recommend-for-nutrition) for more detailed information about nutrition (I've posted a response there listing what I think is good "further reading" material).