The first instinct of most posters on this board is to tell you to run more. In your case, they're probably right.
In track, your 800 time would get you to the state championships automatically. In cross country, you would not make it to the state meet in any of the other three sectionals. Going through by far the weakest sectional in the whole state allowed you to advance in cross country. With the low mileage, it's not surprising that your 800 is very strong while your 3 mile is not at all.
Your 3 mile time at state was constant from last year to this year, about 20+ seconds slower than the PR you listed. For an athlete of your caliber, that time (run on a beautiful day both years with excellent footing) shows that you have a great deal of potential aerobic improvement if you'll run a little more. For the first week, try running twice a day for two days - say Monday and Friday. Then go three days a week - say Monday, Wednesday and Friday. Run easy on the extra run. If you only run 2.5 miles a day (20-23 minutes) you will notice a difference in three weeks. This gradual increase will not drain you of your speed, which is fairly good and will probably improve this year.
If twice a day is a mental or physical drain, then increase the distance of your regular runs.
Then gradually increase your long run.