Paul Rationalizations & Cancelling Commandments

The rationalization which comes about in the books attributed to the Apostle Saul (changed his name to Paul), are full of statements which basically cancel the Torah or Law of the Old Testament. He makes it a matter of how you 'understand' something that makes it 'permissible' or 'forbidden.' As an example in the English Revised Standard Version which I have carried with me since 1953, it says in Paul's letter to the Romans:

"I know and am persuaded in the Lord Jesus that nothing is unclean in itself; but it is unclean for any one who thinks it unclean."
[Rom 14:14]

And again, in the same letter:

"So do not let what is good to you be spoken of as evil. For the kingdom of God does not mean food and drink but righteousness and peace and joy in the Holy Spirit."
[Rom 14:16]

By these types of statements, Paul pretty much cancels the entire Old Testament Commandments.

Yet at the same time, in the same English version of the Bible in the first book of the New Testament, we are told that Jesus preached a message which was exactly the opposite of St. Paul:

"Think not that I have come to abolish the law and the prophets; I have come not to abolish them but to fulfill them. For truly, I say to you, till heaven and earth shall pass away, not an iota, not a dot, will pass from the law until all is accomplished. Whoever then relaxes one of the least of these commandments and teaches men so, shall be called least in the kingdom of heaven; but he who does them and teaches them shall be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven." 
[Mt. 5:17-20]