What are the chances of getting pregnant after having a tubal 8 years ago?

I had my tubes cut tied and burnt in Sept 03. I got pregnant with my son in June of 06. The doctor swore i had a hole in my tubes and that it would never happen again. I was pregnant again in August of 07. I miscarried that baby. The doctor still stuck by his Word that my tubes were still tied it wouldn't happen again. I am now pregnant for the third time since my tubal. Guess the doc was wrong.