Unexplained Shin pain

I have a persisent pain in my right shin at the moment which I can't seem to shake off. Seems to be OK when walking but running aggravates it. It's not excrutiating - just what you might call sore after exercise. It is not localised and you don't seem to be able to pinpoint a specific place that hurts more than any other. Been resting, stretching, and icing it 3 times a day and but I don't seem to be able to shift it - have thought about running regardless but don't want to make it any worse as I have two big Lakes races coming up in the next month or so.

From what I've read, i don't think its shin splints as I'm sure it would be far more painful but struggling for a diagnosis and therefore best course of treatment. Not changed shoes or altered training regime for ages either.
I did have a painful insect bite in the area which caused some bruising and initially I did think it was related to that but surely that would have cleared up by now.

Any ideas?

The obvious thing not to miss is a stress fracture - see your GP for an x-ray - it sounds like you have had symptoms for long enough for the x-ray to be abnormal. It would also pick up any other bone problem - infection for example.

Ooh that sounds a bit serious though now sounding quite possible looking at the symptoms.
Off to the GPs next week it is then (if I can manage to get an appointment out of the gestapo on reception!)