If we say we have sin, when "God hath made Jesus to be sin for us", then we have not yet understood 1 John 1:9, is not doctrine or instruction regarding a believer.
See, its not a good idea to confess sin, that Jesus has taken care of, on the Cross, forever, = "Jesus is the one time Eternal Sacrifice for sin"...
However, because we have a conscience, and because it stings if not obeyed, then there is nothing wrong with having a talk with God, in those times.
So, read 1 John 3:9, as that one is for the born again.
You should be on a game show. You know how to play with words to not admit you sin. We confess to keep fellowship open, not to keep our relationship, which is eternally secure.
And all three epistles of JOhn are for believers! JOhn was not writing to the heathen, but to as he put it:
1 John 2
King James Version
2 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
12 I write unto you, little children, because your sins are forgiven you for his name's sake.
13 I write unto you, fathers, because ye have known him that is from the beginning. I write unto you, young men, because ye have overcome the wicked one. I write unto you, little children, because ye have known the Father.
14 I have written unto you, fathers, because ye have known him that is from the beginning. I have written unto you, young men, because ye are strong, and the word of God abideth in you, and ye have overcome the wicked one.
18 Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time.
27 But the anointing which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.
28 And now, little children, abide in him; that, when he shall appear, we may have confidence, and not be ashamed before him at his coming.
1 John 3
King James Version
3 Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not.
2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
I could keep going, but know this my poor deluded brother- John was most definitely writing to and for believers!