Please try to understand that by confessing your sins to a priest, you will be confessing them to Christ through the ministry of the priest. The priest is not there to judge you for your human failings; he is there to offer you Christ’s forgiveness and grace.
It is also very helpful to realize that you may make your confession anonymously. Confessionals have privacy screens that you can kneel behind to make your confession. More likely than not, the priest will never see your face. If you wish, you can even go to a church where you do not know the priests personally so that your confessor will also not recognize your voice.
Priests hear thousands of confessions during their priestly ministries. No doubt they have heard confessions of sins even more grievous than yours. Not only are priests bound to observe the seal of the confessional even to the point of martyrdom, but priests I have spoken with often say that many times they do not even remember individual confessions they have heard because they hear so many through the years. No matter how grievous your sins, it is unlikely that you will shock your confessor. Even if you manage to do so, it is likely that all he will be concerned with is granting you forgiveness and giving thanksgiving to God for the grace of your conversion.