There is NO NEED for you to apologize. You are asking a GREAT question that demonstrates you are sincerely walking with the Lord closer and closer. That you are asking this question means you are serious about the sacrament of confession and that is a powerful sign of your conversion to Him!
All you need to tell the priest is the Nature and close as possible, the number of the sins. For a large number, take a few moments beforehand and just make your best attempt at an estimate. That means there is no need for you to relate an entire story: just the outcome.
A way many of the saints have looked at confession, (and it sheds light on the tradition of viewing Satan as a kind of demonic prosecuting attorney in the heavenly courts) is to “accuse yourself.” It is said that St. Francis used to accuse himself most severely in confession.
I try to use that approach myself, because it tends to focus my mind on the outcome of my sin: the offense I gave to God. My offense against Him is the bottom line.
Remember: nature and number. Go through the ten commandments–you can’t go wrong with that approach.
• “I committed 16 murders”
• “I skipped mass for 18 years”
• “I purposely led innocents into sin 3 times”
If the priest needs more details to understand the nature and magnitude of these sins in your life, he will ask for more details. Priests are more attuned to sin and confession than you or I will probably ever understand. There is no way to shock a priest in the confessional–it’s the LAST thing you should ever be concerned about.
Try to cover all the bases – all the mortal sins and venial sins that are repeated because unconfessed venial sin can become mortal sin–attachment to sin. But be careful of something called scrupulosity–a kind of pride in refusing to believe in Christ’s forgiveness of our sins. Ask your priest to explain scrupulosity, and how to avoid it.
Don’t get the idea that I’m perfect at it myself or anything like that, but try to remember that examination of conscience is a lifelong process, and like anything else, with practice, you will improve the skill of examining your conscience. But God sees everything, and that includes sins I might decide not to confess. So if in doubt, confess it. If it isn’t a sin and you think it is, the priest will tell you it isn’t.
I find it helpful to say to myself “How did I turn my back on Him today?”
When you make a good confession–come clean–and the priest says “…I absolve you of your sins…” remember it is not the priest, but Jesus who speaks through the lips of his priest saying those words. This is so critical to understand, that if a priest were to say something other than “…I absolve you…” the sacrament would not be valid. This has happened to me before – watch out for it. It also makes a better argument for always going to the same priest, too.