From what I have researched the greek word porneias which is used in this scripture verse can mean several thing all dealing with being sexual in content including prostitution, adultery or an illicit marriage or relationship. The Vulgate says "except for fornication". The RSV says "except on the ground of unchastity". KJ "saving for the cause of fornication". NIV "except for marital unfaithfullness". Douay-Rheims "excepting for the cause of fornication". So there is no doubt that we are dealing with an illicit sexual relationship. Also seeing that the word porneias is being translated to fornication in many bible versions, the definition of which is having relations before marriage how does this play into the verse? So I suppose the real question is, is divorced allowed when Jesus in so many scripture passages is very stongly against it? Could it be that the divorce being allowed is similar to when Joseph was going to quietly divorce Mary who was betrothed to Joseph but they had not yet come together and that after a marriage is consumated divorce is not allowed?
The meaning for the Greek word porneia is "harlotry (including adultery and incest); figuratively idolatry: - fornication." The word was used for a sexual act with other than your given spouse. This word is never used in the relationship between husband and wife.
In reference to Joseph.
Mat 1:19 Then Joseph her husband, being a just man, and not willing to make her a publick example, was minded to put her away privily.
This is not talking about a writ of divorcement. It says that he was going to put her into privacy so that no one would see her and know that she was pregnant.
The answer to the question "So I suppose the real question is, is divorced allowed when Jesus in so many scripture passages is very stongly against it?" is found in the following verses. It was due to the hardness of their hearts that it was allowed.
Mat 19:6 Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.
Mat 19:7 They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away?
Mat 19:8 He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so.
Even in Jeremiah we see divorcement mentioned in reference to adultery.
Jer 3:8 And I saw, when for all the causes whereby backsliding Israel committed adultery I had put her away, and given her a bill of divorce; yet her treacherous sister Judah feared not, but went and played the harlot also.