Shin splints can be caused by a few different things one being the length of the gastrocnemius vs soleus. If one muscle is stretched more than the other this causes and imbalance that can cause shin splints. When you stretch make sure to do both a straight and bent knee stretch.
Also since you already are feeling the symptoms I would suggest getting a laccross ball or something similar and doing this. Take the ball on the outside edge of your tibia and press the ball into the muscle then roll the ball out to the outside of your shin. Start at the top of your shin and work all the way down to the ankle doing this movement.
For the inside of the tibia use a little oil and press your thumb into the muscle then slide down the edge of the tibia to the ankle then work back up to the top. If you can stand it rock the pad of your thumb back and forth working from top to bottom and back up again.
I'm going to tell you, this sucks. It is not pleasant by any means but it does work. After you have done your self massage drink lots of water to keep the muscles from adhering to each other again and continue to do both the straight knee and bent knee stretch.
Repeat this every couple days until the shin splints go away.