Can I sleep with a girl when in a relationship break?
Have you slept around while not on break too?
Yes. I was sleeping with other girls while being in this relationship before
Well, for starters you shouldn't be sleeping with anyone but your partner while in a relationship. Even if you're on a break they may not be okay with you sleeping around.
I do not trust her at all. I feel like this break was a good idea. She better not be sleeping with someone else on her break.
It doesn't sound like your break rules are very transparent. You should have a talk and make sure you're both okay with whoever is doing what, even on a break. That way you both can be on the same page and not be upset over the relationship.