The Sexual Act And Christian Teaching

hey what i believe is once its the bond (marriage) between man n woman then how they have their sex does not concern us.
once the two of them are fine with themselves whether oral or anal or the coneventional (missionary position) or anyhow they deem it suitable and enjoyable to them, then there is no problem.
But when sex is out of wedlock, there you have a problem with christianity.
any other form of sexual act out of wedlock also is sin.