Chest Pain at onset of exercise and subside over 15 minutes

For as long as I can remember I've had sharp right/center-sided chest pains at the onset (within 5 to 10 minutes) of runs but subside after 10 to 20 minutes.
I'm 24 years old, 5'10'', 145 lbs, have had no heart related medical problems, low HDL, and good blood pressure. Currently I'm running about 50 miles a week at about 6 to 6.5 mph.
What's interesting about the pain is that if I continue on my normal 8 to 10 mile run at 6 MPH the pain slowly subsides and then almost dissappears by the end. It's most intense between mile .5 and mile 3, but if I push through it at the same pace it goes away. Also, I've noticed that if I try to run 10 miles at even a slightly faster speed than I am accustomed, the pain comes on much worse and will not subside until I decrease my pace.
It's frustrating because I feel like my legs and body can easily run the 10 miles at 7 or 8 mph, my chest simply won't let me do it. Conversly, if I jog slowly / walk rapidly the pain is altogether absent throughout.
Any thoughts on what this might be, if anything? Any suggestions on treatment?
Thanks.