Just some background information to work off of:
I am a 20 yr old male, 6 ft 185 lbs, I have an athletic build. I have been running for about 4-5 months now. When I run I try to land (strike) with the middle of my foot, and I tend to run very slow (11-13 min miles). I am currently training for a triathalon where I will have to run a 10k.
I usually try to run 4-6 miles at a time when training, but my runs are anything but consistant. One day I will go 5 miles at an 11 min pace, and the next day I have to run 13 min miles. The reason is that generally about 1 mile into all of my runs my legs, specifically the outside of my shins (tibialis anterior muscle) starts to hurt so much that I have to stop running, or struggle and endure the excruciating pain, which doesnt really die down much. Now I don't think that the problem is that my legs are not strong or in shape. I am very athletic and sometimes I can go for a run and my legs barely hurt (this is very rare). The pain is worse some days than others.
As far as stretching goes, I avoid static stretches before I run, I generally will do some buttkickers, and calf raises, and I build up to each run starting from a walk. Any advice would be appreciated, thanks guys
Okay, first the good news, you're in good shape.
Now the bad news; your in good shape, and that usually spells I-N-J-U-R-Y for new runners. Why? Because while your legs may well be strong and agile, they are very poorly conditioned to endure the rigors of running. The only thing which can condition your legs for the indignities visited upon them from running, is running, running, and more running. Among those I coach, folks already in good shape when they start running have the highest likelihood of getting injured. Why? Because their overall level of fitness allows them to run faster than the underlying infrastructure of their bodies is ready to support; specifically the bones, joints, legaments, and tendons. To take it one step further, shin splints (what I believe you are suffering from) is the number one injury I see in folks in good shape who start running.
Advice, slow things way down and build your mileage base; don't worry about trying to speed things up until you can consistently run six or more miles at a slow pace without any pain.
Fat old man PRs:
Shin splints are not uncommon in new runners, and the problem is that once you have them, they are hard to get rid of. In my experience, they result from running faster than your legs/body are in shape to run. This has little to do with general conditioning or how athletic you are. You have some signs of hope in that you can sometimes run pain free. My guess is these are more casual runs, where you start off and continue at a relatively slow pace. Shipo's advice is basically sound - run at a slower pace that allows you to run without pain. As you gain experience, you should be able to feel your shins start to ache when you pick up the pace, and you will know to slow down.