Peace Nick,
The NAB gives valuable commentary on these verses.
5 [12-13] Everything is lawful for me: the Corinthians may have derived this slogan from Paul's preaching about Christian freedom, but they mean something different by it: they consider sexual satisfaction a matter as indifferent as food, and they attribute no lasting significance to bodily functions (1 Cor 6:13a). Paul begins to deal with the slogan by two qualifications, which suggest principles for judging sexual activity. Not everything is beneficial: cf 1 Cor 10:23, and the whole argument of 1 Cor 8-10 on the finality of freedom and moral activity. Not let myself be dominated: certain apparently free actions may involve in fact a secret servitude in conflict with the lordship of Jesus.