Jesus died for all our sins past pesent and future once and for all. That's common sense and obvious enough becos when he died for us, we were not even born yet, so of cse all our sins had to be future when he died for us.
This idea that you are forgiven of only past sins when you got saved is illogical. Think abt it: If that were true, it wld mean that you have to make sure you confess and receive forgiveness for EVERY sin from the time you are saved to the time you breathe your last, becos if you don't it wld mean entering heaven (or hell for those who believe OSNAS) with unconfessed/unforgiven sins. It's simply not possible to confess every sin you commit -- anyone who thinks that's poss is simply kidding himself.
And the whole idea of confession (of sin) is wrong. When you sin, you DONT confess what you did wrong. You confess your righteousness in Christ. CONFESS in the Greek means "same word" ie say the same word with God (who else!) regarding your sins -- that he remembers them no more and doesnt impute sin to you everytime you sin! -- that is a BASIC witness of the Holy Spirit!
So when one sins, he is to confess his RIGHTEOUSNESS IN CHRIST, that God remembers no more and that it is not imputed. He is to thank God for all this becos of Jesus' finished work and then move on!
Its so simple:
When we are sick, we dont confess our sickness but our healing. We say the same thing God says about our sickness -- eg By His stripes we are healed.
When we are in lack, we dont confess our lack but our prosperity -- The Lord is my Sheperd, I shall not be in want. And my God shall supply all my needs according to his riches in glory.
So, when we sin, why confess our sins the traditional way? That's not the antidote to sin. that's a negative confession. No, say the SAME THING GOD SAYS ABT YOUR SINS -- forgiven, forgotten, not imputed!!!
Once I repent (turn around and don't do it again) they are no longer held against me. 
If I do not repent of a sin, I have KEPT that sin from Christ and thus from forgivness.
