Masturbation is also called self-abuse. Sometimes it is easier for people to say they commit the sin of self-abuse than to say masturbation.
It can also be called solitary sin, or a solitary sin against chastity.
Also, remember that in confession we must not only say the specific type of sin (species) but also the number of times we fell into that sin.
If the sin was while looking at impure pictures or video images, this should also be mentioned.
As with all sexual sins, one should never be graphic or overly detailed. What matters is listing the species of sin, and the number of times the sin was performed.
It is also important to add factors that modify the sin, for example if someone is married (meaning that their sin wasn’t just fornication, but adultery), if the penitent is a priest or religious, engaged, in the habit of a particular sin, if the act was alone ore with others, if the penitent caused others to sin or tempted others, if the activity was with someone of the same gender, if the action involved a minor or a relative, etc.
Say what you did and how many times you did it in a clinical way and then honestly answer any questions the priest has. No explicit details!
It can also be helpful to let the priest know if you were drinking or under the influence of medication (or illegal drugs).
For your own sake, you should pay attention to the times you fall into this sin. Is it when you are idle too long? When you are stressed? After watching suggestive television shows or movies or listening to suggestive music? Perhaps it is after being with someone you are attracted to?
You get the point.
If a priest tries to tell you that masturbation is healthy or normal or not considered a sin any more, know that he is wrong and not in line with Rome on the matter. Don’t bother arguing. It won’t help. List other sins and get absolution, but try to confess to a Catholic priest who is actually faithful to Church teaching in the future, i.e. actually Catholic.
It may be that the priest says that your sin was not mortal because it didn’t involve sufficient reflection or full consent. That may be true.
But if they tell you that it is okay to commit the sin of self-abuse and that it’s common, normal, or healthy, avoid that priest.
As for being embarrassed, besides the fact that solitary sin is probably one of the most commonly confessed sins, it is better to be uncomfortable for a minute or two than to lose your soul and suffer forever. It would be silly to trade your eternity just to avoid emotional discomfort. Besides, I seriously doubt the priest is going to flip out and browbeat a sincere penitent Catholic in the sacrament. If they do give you a bit of a hard time, it isn’t meant to humiliate you, but to help you.
Get it off your conscience! Get to confession! It’s important to your eternity.
Finally, every time we confess our sins and deliberately neglect to confess a serious sin we are conscious of having committed, none of the sins confessed are forgiven, and the confession itself is a sin of sacrilege. If we walk into the confessional with four serious sins to confess, and we deliberately withhold one sin in the confession, we walk out of the confessional with five serious sins: the original four, plus the added sin of sacrilege.
Don’t leave out serious sins on purpose. Just spit them out and be done with them! Better to be uncomfortable now than to burn forever!
Above all, remember that Jesus loves you and wants you back. He is calling you to the sacrament of reconciliation in order to draw you closer to Himself and lead you to heaven. He is there in the sacrament, ready to pour out an ocean of mercy and work the miracle of bringing a soul dead through sin back to life. There is no sin we can commit that God can’t forgive. Nothing is more powerful than God. If we think He can’t forgive us, we believe we are capable of sinning in a way that id more powerful than His mercy.
Remember that we have to actually be sorry for the sin and resolve to avoid the sin in the future. We have to have a firm purpose of amending our lives. If we intend to sin again, we can’t be forgiven. We may know we might fall again, but we have to be making an effort, and we should go to confession as often as we fall. Those are signs that our hearts are in the right place.