Question: What is it? Is sex just for pleasure with your partner breaking a precept? Eg with a condom. And is being circumcised bad over personal preferences/ (hygiene,aesthetic)? is oral and anal sex bad? Is masturbation bad? And is circumcising your sons bad?

Answer: 
Sexual misconduct is defined in the Pali scriptures as having sex with someone else's partner or fiancee and with those living under the protection of their parents or an institution (in the case parents, if the parents disapprove). 

The purpose of refraining from sexual misconduct is to not harm/damage existing relationships. 

Therefore, having sex for pleasure, using a condom, circumcision, masturbation & oral & anal sex are not, in themselves, sexual misconduct (even though some of these things can be unwholesome & unskilful).
Ideally, sexual pleasure should be avoided since it is craving. But Buddha knew that this was difficult for the laity. Therefore, he suggested that the laity should avoid sexual misconduct. Sexual misconduct is simply sexual behavior which is outside social acceptance. And you can interpret that according to your own society.