Well played, use SEX in the title then transition into preaching. Putting your belief system aside if your unwilling to have sex and your partner wants a sexual relationship you shouldn't be pressured. If it ends the relationship, well it wasn't going to work out anyway.

That said, your choice to have sex or not is yours, remember only you have to live with the consequences, including regretting not doing it. You can use dogma to guide your choices but your the one in control.