Recently, began to happen that the condom is actually weak protection. Allegedly latex's pores are too large, and between them are easily scattered as spermatozoa and different infections and viruses. Yes, and condoms are often torn.
In fact, these guesses are far from reality. The condom is a product consisting of many thin layers of latex. Pores in the layers are combined in such a way as not to overlap on each other. As a result, there is a strong "armor", through which no non-crushed guest is slipped.
Condoms are not so often. According to statistics, 98% of them reliably execute their function. This result can not guarantee any other contraceptive. By the way, pulling two condom is not smart. It will only increase the chance of rupture. Take one, but high-quality and suitable partner in size (many manufacturers have condoms of different "capacity").
In order to insure itself from herpes and human papilloma virus, ask the partner to put on a condom and in front of oral sex.