I cheat on girls I date so if they do it to me I'll already have gotten them back
Why do you think that you should cheat on them?
Because this is a fair and right thing to do. I don't like to be cheated.
Cheating on them first may be why they cheat on you. Relationships should not involve this and find someone who doesn't cheat so you don't feel you need too.
I just didn't like her body.
If you do not like something about her, then you should leave her. There is never a good excuse for cheating on a person.