I am thinking you might want to start with your shoes. As you said, treadmills are a very forgiving surface to run on because they are flat, plus they have some give to them. If you have not already done so, go to a mom & pop type running store (NOT a big box sporting goods store), or a Fit2Run if you have one in your area. The folks in true running stores have people who are trained to fit you to the proper shoe for your gait.
You can work on adjusting your gait, but if you do so, you should do it by slowly working up to it. In the meantime, you'd still be dealing with ankle and shin issues, so you need to address the immediate problem, which may be the shoes. Once you have changed your gait, then return to the running store to make sure you're still in the right shoe.
If the running store says you are in the correct shoe, consider how many miles you have put on those shoes. Most shoes start breaking down somewhere around 200-300 miles, depending on what shoes you're running in and how hard you are running.
Good luck. I hope you find the answer to your problem. Let us know what you find out.
"God gave you your body as a gift, so you should take care of it." - My Mom