Paul is really comparing two things here. He is comparing what I was to what I am now. I was dead, but now I am alive in Christ. Before I came to know Jesus, my sins were unforgiven, but now that I am in Christ, my sins are forgiven. This certainly seems to say to me that all of my sins are forgiven. That would include every sin in my life, whether they are sins of my past or any future sins.
Dr. Fred has written numerous books and articles that cover a wide-range of theological topics and he endeavors to present the study of God's Word in a clear fashion, helping the average layperson comprehend the great truths of Scripture.