Whilst I can't really advise you on your specific problems, hopefully my current, and hopefully past problem will help you make an inormed decision on what to do.
I have been running for just over 3 years, and up until last April was making the embarrassing mistake of buying trainers from a normal sports shop. I say this as I found out that I was a heavy over pronator. As a result I developed shin splints and all sorts of other nasty injuries, which manifested itself by my leg going numb, my shin seizing up, and my foot 'slapping' on the ground, due to lack of control/feel. I also suffered from a numb/intense pain in the shin. I am now going to an absolutely fantastic sports physio in Chester, who is also a runner and knows exactly what I am going through. He has done a number of things for me. - Ensured I am running in the correct trainers. - Is making reinforced hardened foam Orthrotics (which are a damn sight cheaper that carbon fibre) - treated the injury, with sports massage and ultrasound - Treated the issue behind the injury, which was identifying my running style, and strenghtening up the relevant muscles in my legs and ankles. Personally Paul, I recommend you track down a decent sports physio in your area to get them to look at your injury, and the causes behind it.