I am a priest.
For Grace 68, yes, have a priest that you can talk to about it - I understand your concern, and even your worry, it can have a big impact on your marriage if you don’t get good answers. I have never hesitated to help people with exactly this question, some times in confession, some times in spiritual direction, some times in just conversation. It is an important question and so it is fair to ask; here is not the time or place for that though.
You will be surprised at how comfortable a priest will be with such discussions.
For Turtle18
“Self gratification” is going to mean something to the priest in the confessional that you don’t mean to say. From the way you describe it here, no priest could be certain if there is mortal sin or not. Saying “self-gratification” is certainly intimating mortal sin (if you came to me, I would ask a question or two to help you figure out how to confess this and maybe deal with those occasions when this sort of thing happens to you).
The advice about stating category and number is ok I guess, since the priest would then be inclined to ask questions to know what he is forgiving or retaining (Jn 20:23). For example, catgory: impurity, is not enough, there are a million variations and the priest needs to know what sin he is dealing with here. So in the end, while that advice might get you where you need to go, it is not really the best way to make a confession.
My advice to turtle18 is to tell the priest “I was doing some exercises and found myself aroused.” If you want to tell him what came of that (you stopped, you said a Hail Mary and the arousing stopped, so you finished your exercises without a problem, whatever), that would be helpful. But he has heard it all before, and he will take it from there - asking about intention or consent, or if it went beyond just being aroused, etc.
“Self gratification” is not really accurate - it sounds like mortal sin, when, as I say, what you described here does not.
“But it’s too embarassing to bring that up to a priest,” you said. Don’t let the devil and pride stop you from saying what needs to be said. “Too embarassing” is a poor reason for not making a confession as well as you can - priests have heard things you never even dreamed of, and God gives us the grace to hear it and talk about it if necessary because it is what we are there for - to heal and help heal souls.
Fear is from the devil, be not afraid.