For mortal sins, yes, you must go to confession.
Venial sins are forgiven through MANY ways (Holy Communion, blessing yourself with holy water, saying the Confiteor, praying the Act of Contrition or Our Father, any sincere prayer, striking your breast, reception of ANY sacrament in the state of Grace, receiving a bishop's blessing, receiving the Pope's blessing, among many others) BUT it's most important you are sorry for them.
It's important to confess any venial sins if you don't have any mortal sins to confess. Many do a devotional confession, where they confess many venial sins.
MOST IMPORTANTLY: Catholics do NOT believe works save you, it's the grace of God which saves you. Good work are basically stating you are already saved and you are working out your salvation with fear and trembling.
You CAN NOT earn your salvation. It's a free gift.