Sat nam. That's because Guru never gave us specific guidance on contraception or on sexuality, so others have since tried to fill it in. So some Sikhs see contraception as un-Sikh, others see it as OK. It should be a personal decision of the couple involved, in any event.
As for sexuality, the only references to this in Siri Guru Granth Sahib are ones that decry lust, one of the 5 vices. Lust is not ANY sex. Lust is a reference to those who focus only on sex or use sex in non-marital situations, such as employing prostitutes or having affairs outside of marriage. Lust is the objectification of sex.
I'm sure you've found in articles that some Sikhs regard the vice "lust" as any sex, i.e., to include legitimate sex between husband and wife. This is an inaccurate portrayal of the matter; all but one of our Gurus had wives and children. The Sikh path is the path of a householder (married person).
You should probably not try to conclude what the Sikh views of contraception and sexuality are, so much as show the range of viewpoints because of the lack of specificity. And be careful not to mix up Indian/Punjabi or Western traditions of either with what is in our Guru and Rehit.
Guru ang sang - DKK