In reply to Markhoss:
Well now, that is a post from someone that's a bit near the edge. A bit concerned and a lot confused and thinking that's a bit of a mess; no worries, these things can all be sorted. It'll take effort and you'll need to commit to it, but it can be done.
So, two groups of things: what you do and what you think.
What you do is the easier one: don't overtrain. Give yourself a routine, stick to the routine. Day one, four miles jogging, day two six miles running, day three four miles flat out, day four rest, day five four miles jogging, day six eight miles running, day seven rest. Repeat. Adjust distance and speed to suit you but keeping in the same pattern, don't move the rest days. Stretch, warm up, then stretch again when you're done.
What you think is wrong thinking; if you can't do one thing then you won't be able to anything. Google thinking errors, learn about them, challenge your negative thoughts the way you challenge yourself when running. Tune in to the part of your brain that's a critical friend, that examines what you think and tells you when you're taking a mental wrong turn.
If it persists, do see your GP. But also post here; lots of us have been down similar paths and are always willing to lend a hand to those that are suffering.
T.