Please don’t take offense with what I am about to say. It may not be your situation, but I am just throwing it out there.
Are you saying that you go to confession each week because you are committing mortal sins each week? There is such a thing as abuse of confession where people use it, in some way, as a way of justifying (that’s not the word I am looking for), continuing to commit mortal sins knowing you can go to confession on Saturday and receive on Sunday. They are not really looking to give up that sin. In order to have a good confession we say we will work to avoid sin and temptation. One of the benefits I have found of frequent confession is that I don’t commit particular sins anymore.
I would think that people who go to confession weekly are either struggling with a particular mortal sin, or are practicing devotional confession, which is fine. If a person is committing a mortal sin weekly, so much so that it interferes with a liturgical ministry, then they should reconsider serving in that particular ministry until they get a handle on their particular sin.We are called to change our lives, to consistently look at our sinful lives and repent and sin no more.
Also, are you sure what you are confessing is actually a mortal sin? Many people who are scrupulous think they are committing mortal sins when in actuality they are not. It might be a good idea to talk to your confessor. Do you go to the same priest all the time? If not I would suggest that you do so that he gets to know that pattern of your sin and help you to avoid your mortal sins.