welcome!~ wow!.... 4-5 miles a day thats great! I wish I were that driven, that's awsome!
I have read of alot of people going off of it! they have a life after phen divas forum on here of women who are no longer on the phentermine and trying to maintain weight loss! you might ask one of them.
and I think your right about wanting to get phen from your Dr. selling perscription drugs online is illegal and i have read of alot of people buying on line and it not being real phen!
I bought a BP cuff and a digital scale and now my dr. lets me call in my monthly weight and BP and then she calls in my perscription, you might try that,

well good luck~
on phentermine 37.5 mg "Qualitest"
in june I was @ 278lbs biggest ever
aug, 26, 08 @ 264 lbs started phen
aug, 31, 08 @ 255
sept, 05,08 @ 251
sept, 09, 08 @ 249 woo-hoo!!!
sept, 11, 08 @ 248
sept, 12 08 @246
sept, 30, 08 @ 241 slowly but surely!
nov,10,08 @ 236 lbs
nov,12,08 @ 234lbs
nov,13,08@233lbs