So my last perod was October 9 and I went to the doctors to confirm my pregnancy and let me know how many weeks I am, and they tell me my due date is August 17 and that I'm 29 weeks pregnant. If I really am due on August I would be pregnant for 10 months. I also go to different websites to check if its right and it come out to be that I'm 33 or 34 weeks pregnant I'm really confuse.

Dates are all Best Guess and only an indicator at most.
Your child will arrive when they are good and ready, so there's really no need to stress.