If you are running on a relationship that is based on sex, I doubt you think it will go somewhere far, but eventually you will want to go somewhere with a person.. Eventually that will get boring and repetitive and you and your partner will decide to go separate ways. Up and down on it goes like that, and this is how most people spend their time with other people, especially at an early age. When seeking out a partner, try to not focus on the sex as much as possible, or it will get really hard to tell if you have actual feeling for that person.
I know this seems crazy to some but it is definitely worth it, eventually if you continue at your old game you will get burned out and tired of constantly dating and having it go nowhere each and every time. It take discipline and time to get to this point in understanding, so I recommend you start as early as possible and you will get there..