How's your sleep?
If you find yourself going to sleep easily, then waking up in the middle of the night and having a lot of trouble getting back to sleep: that's a classic symptom of overstress. It doesn't help that overstressed people often consume a lot of chocolate and other caffeinated food/drinks--which will disrupt their sleep further.
Not much help to you now, I realize, but get in the habit of counting your pulse for a full minute when you wake in the morning. Once you know what your baseline pulse is, you can use an elevated morning pulse as a rough guide to whether you've recovered--anything 10%+ above your norm is a sign to go very easy that day or take the day off. (Exception: don't take your pulse on race days! It will often be elevated, just from nerves, and you don't want that kind of feedback.)
Be very careful with doing cross-training, unless it's a familiar activity that you've done with some regularity recently. If you're overstressed (= adaptation reserves depleted), the last thing you should do is to introduce a new thing to adapt to.
But in general: if you can get an extra hour of sleep per night (I bet you can if you really try), and sleep at regular times every night (including weekends!), you'll probably start to feel peppier. Until then, keep your training light and avoid anything new.