Groin pain AFTER run

Question
I am 40, 6 foot, and about 180. I run 5 miles a day up to 5 days a week as work/life allows. My normal run is indoors on an 1/8 mile rubber track with no banking. Direction reverses each day. I normally run the 5 miles in 34 to 37 minutes. I spend 1/2 a mile warming up and about 10 minutes cooling down (walking). My problem is that my groin (both sides) seems to get quite weak after I stop and get dressed. It is actually painful when I get out of the car after I drive home (about 30 minutes after running stops). Any hint of pain goes away within an hour of getting home most days. On days it lasts longer, I have usually mixed in some 440 speed work. On days that I mix in stair work, I rarely have any post-run groin pain or it is very short. I have a strong feeling the issue is lack of specific groin stretching before and after running as well as groin/core strength work but thought I would ask anyway. Thoughts for an amateur?

Answer
Right off the bat all I can say is to see a doctor. This isn't a normal running thing, it sounds like something is wrong with you.

Just to throw in something about your training; maybe you need less straight running and more strength training to compensate for your weight. 180 isn't too much, but maybe you need to gain some muscle before you start doing regular running. This is usually not how training works, but your case is weird anyway.
In the first place I don't see how lack of core strength affects your running so much, you would have to be very strangely undeveloped in your core for these weird pains to be occurring. I've never heard of anyone having this problem. The best way, if a doctor doesn't know, to fix your problem, is to learn from it. You sound like you are smart enough. Just look at it, analyze, and learn why it happens. And then fix it. It always takes work.

Good luck
Jared