Is using two condoms better than one?
No. Using two condoms at the same time is a bad idea, as the rubbing or friction between the two may cause one or both condoms to tear.
If you want to take extra precautions against pregnancy or diseases, it's better to use both condoms and another form of protection. For example, you could use both a condom and the birth control pill, Implanon (a contraceptive implant), or Depo Provera (a contraceptive injection), etc.