I'm going to stop sex in the middle of it
Why do you wanna stop in the middle?
I get distracted by other things going on.
It is ok to stop having sex if you don't want to. You should not lead people on if you are busy with other things it is kind of rude.
If they are not satisfied they can find someone else rather than complain to me.
I hope your partner will understand so you don't need to worry whether they are getting satisfied. Maybe you should talk to the and explain the situation.