It's called moral character strength. Decide which girl you really want because having BOTH is not an option. Make that choice & break it off with the one yiu choose not to be with.

If you don't & they find out, you will probably end up with neither. Cheating is never acceptable when you have committed to being with one person (I am not refering to marriage but an exclusive relationship.)

I would spend less time feeling guilty & more tkme defining my moral values.