My Dog Was Mated 8 Days Into Her Season. Now She Has Stopped Bleeding. Has She Fallen With Puppies?

Cessation of bleeding does not mean she is pregnant.  The earliest and most reliable way to diagnose pregnancy is via ultrasound.  The earliest fetal vesicles can be seen is day 20-22 and more reliably at day 26.  Uterine enlargement can be palpated as early as 3 weeks.  Fetal skeletons calcify at day 45 and can be seen on x-rays.  Radiographs are the best way to estimate the number of puppies.  
At this point it is just a waiting game.  When she may be ~3 weeks along have her examined by your veterinarian and ultrasounded.

Every female dog has a period like humans. But they also will last 7-14 days for dogs. At  the end they will stop bleeding whether they are bred or not. If you don't have the money for a vet visit then you should wait, and in about 3-4 weeks you should see her gain a little weight. But don't worry yourself too much, cause it may be 5-6 weeks before you see the weight gain. If you do have the money for an expensive vet visit then you can bring her into the vets office and have her evaluated at about 4 weeks. But make sure you count the weeks!

First time having mated my dog. My Boston Terrier has locked up 2 times that we know of. I still see blood but the scads of males not longer linger . Is that normal?