Whether you are sexually active (having intercourse), want to be, or have been having sex for a while, it's really up to you to talk about birth control with your partner unless you are ready to be a daddy. (And, even then, you should talk to her about whether she wants to be a mommy.) Don't assume she's on the pill or that "pulling it out in time” will work.
Sex is fun and should be, but it can have negative parts as well. Babies and STDs are no joke. You should take the time and find out about the different types of birth control that are out there and how well they work. It can be fun to do this with your partner, then you can make smart choices together. Using birth control that works makes sex even better because you're not worrying about getting your partner pregnant.
An effective birth control method for men is condoms. You can learn how to put one on. A more effective birth control strategy is to use a condom at the same time that your partner uses a spermicide like contraceptive foam, suppository or gel. Using these two methods together also helps protect you both from getting STDs too!
If you are positive you don't ever want to be a dad or are done having children, there's a permanent birth control for guys – vasectomy. It's a simple, quick procedure that blocks the sperm from going into the semen. You still ejaculate or cum, but there's no sperm in the semen. You don't lose your desire or ability to perform, you just lose the sperm!