No-one has a right to tell you how often to go to confession, only your conscience (informed by your nightly examination) can tell you how often you should go.
If it feels right to go once a week, then do so - even if it is frowned upon in your Parish.
If after a nightly examination of conscience you feel you have indeed committed mortal sin then I would recommend meditating upon and reciting an Act of Perfect Act Contrition (some examples below) and then going to confession at the earliest opportunity…
Acts of Perfect Contrition
- My God, I am sorry for my sins with all my heart. In choosing to do wrong and failing to do good, I have sinned against you whom I should love above all things. I firmly intend, with your help, to do penance, to sin no more, and to avoid whatever leads me to sin. Our Savior Jesus Christ suffered and died for us. In his name, my God, have mercy
- O my God, I am sorry for my sins because I have offended you. I know I should love you above all things. Help me to do penance, to do better, and to avoid anything that might lead me to sin. Amen.
- O Lord Jesus, lover of our souls, who, for the great love with which You loved us, willed not the death of a sinner, but rather that he should be converted and live, I grieve from the bottom of my heart that I offended You, my most loving Father and Redeemer, to whom all sin is infinitely displeasing, who so loved us You shed Your blood for me, and endured the bitter torments of a most cruel death. O my God, my infinite Goodness, would that I never offended You. Pardon me, O Lord Jesus, as I most humbly implore Your mercy. Have pity on a sinner for whom Your blood pleads before the face of the Father. Amen. 4) O merciful and forgiving Lord, for the love of Your, I forgive all who have ever offended me. I firmly resolve to forsake and flee from all sins, and to avoid the occasions of them, to confess, in bitterness of spirit, all those sins which I committed against Your divine goodness, and to Love You, O my God, for Your own sake, above all things and for ever. Grant me grace so to do, most gracious Lord Jesus. Amen.
In all of this, remember God is Love and He understands you, there is no need for being over-scrupulous and worrying over every little venial sin. But mortal sins are to be acted upon as soon as possible.
Here is a useful link on examination of conscience and confession etc, there is also a link to a list of common mortal sins which is very useful at night prayer also.
catholicdoors.com/prayers/consc.htm
God Bless,
DD