Greetings in Christ,
It is normal to feel anxious and nervous when going to confession. Don’t let your feeling hold you back!
From my own experience, I have realised that I tend to feel very anxious because I am ashamed of my sins. It can be difficult to admit to someone (for example a priest) the sins we have committed, especially if you think the sins are “taboo”.
This is how I managed to overcome anxiety when going to confession:
I highly suggest going as regularly as you can so that over time you’ll get used to the feeling you might get. Additionally, if you find a priest you like, try going to him each time you receive the sacrament of Reconciliation, as you will be in a similar environment with the same person each time you go (that way you feel less anxious).
The number one thing to keep in mind is that in the Sacrament of Reconciliation God judges your heart, not your words. If you’re truly contrite of heart, God will forgive your sins even if you fail to mention them (so long as you don’t purposely hold back any sins). It is best to confess mortal sins first and if you find that you forgot to mention something, you are still forgiven. However you should confess what you forgot to mention the next time you receive the sacrament. Hope this helps! I’ll keep you in my prayers that your next confession goes well.
God Bless