First, welcome gigi!
i mean yeah it's a sin in Gods eyes to "waste the seed" as the scripture says (which also supports the controversy on using condoms -ABSTINENCE is truly the way to go seeing as our body's belong to Chris), but what i think Ravi wants to know is what exactly is appropriate sexual behavior in the marriage
I was looking at Onan's act as inappropriate sexual behavior in marriage. But your point is well taken.
You are 100% right about ABSTINENCE.
i used to wonder about this as well seeing as i married while a prodigal daughter and also my husband was not saved until recently (Praise God)
Praise God for His grace!