Late reply, also I'm a guy too so life experience wise, probably not so helpful. A few years back I used to run long distance cardio and looked like a t-rex in body composition. I always noticed a severe lack of energy and cramps/chills/hypoglycemia/hypothermia after going longer than 15 miles. But some days I would get the same symptoms from even 6 miles or less, and I would just end up walking a great deal whenever I lost my energy. I couldn't explain it really. Now words for the wise, I'm about to sound ignorant to the intellectuals here. But as far as I'm concerned, repeated cardio without breaks is just plain harmful for the body. Even with good diet, back to back cardio days just aren't productive besides mental benefits. I'm a firm believer that cortisol and stress wrecks your gains anyways and there's very little benefit to working out unhappy.  Diet wise I'm assuming you're not working out with less than half a tank or at least filled up a little gas for the engine (I view food and fuel synonymously), and maybe using caffeine or some sort of metabolic enhancer/supplement to lower excuses and increase results.  If these words/experiences somehow resonate with you, i guess we might have had some things in common. I would diagnose you with over working and being hormonally imbalanced from over exercise. What I did was incorporating a ton of stretching and herbal supplements, but what you choose to do is up to you.  If your sex drive is nonexistent, getting inconsistent sleep and running out of energy mid way through a workout, it's probably time to perform maintenance and checks.  For a guy I'd remind him that cortisol production and testosterone production are mutually exclusive and stress kills your energy.