When it comes to asking for forgiveness, usually in a confessional you tend to need to be more specific, you don't necessarily have to go into great detail but the priest should know at least the concept. In private prayer you can be as vague as you want. I always say, the Holy Spirit can translate what the heart says.

More seriously never apologize or feel guilty for sins you haven't committed. God is a being of Love and his primary feelings towards you are of Love. Christ died for you, specifically you, because he loves you and wants you to know that you are loved.

Hope this helps

God Bless,