You do realize that Paul was talking of his spiritual journey from having a live sinful nature to being crucified with Christ so that he went from...no longer I but sin in me....to...no longer I but Christ lives in me.
You are close, but your timeline is off.
In Romans 7, Paul wrote, speaking in the present, well, you just read it . . .
Roman 7:17-20 KJV
17 Now then it is no more I that do it, but sin that dwelleth in me.
18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
19 For the good that I would I do not: but the evil which I would not, that I do.
20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
You are conflating this with the Galatians passage.
This is how we overcome our flesh, by remaining in the Spirit. Even so, as Paul clearly teaches, our corrupted body of flesh remains for now (the body of this death).
You need to be able to understand where Paul says that it's no more him, indicating transformation ( it was him, but is no longer), while still professing that sin remains in his body.
Keep this in context, which comes after chapter 6, where Paul explains that transformation in much detail. You are taking what Paul squarely places within regeneration and making it as it were not.
Much love!