I agree we are a new creation; not a patched up one.
However, I disagree that Paul is referring to what he endured 'before' Christ.
(still you make a good point, and one I am considering)
The old man is interpreted as the former way of life, that of an unbeliever. In this sense, the Christian has two competing capacities within him—the old capacity to sin and the new capacity to resist sinning. The unbeliever has no such competition within; he does not have the capacity for godliness because he has only the sin nature. That’s not to say he cannot do “good works,” but his motivation for those works is always tainted by his sinfulness. In addition, he cannot resist sinning because he doesn’t have the capacity to not sin.
The believer, on the other hand, has the capacity for godliness because the Spirit of God lives within him or her. He still has the capacity for sin as well, but he now has the ability to resist sin and, more importantly, the desire to resist and to live godly.
14. For we know that the law is spiritual: but I am carnal, sold under sin.
'am' = eimi in Greek = to be, to exist, to happen, to be present.
17. Now then it is no more I that do it, but sin that dwelleth in me.
'dwelleth' = oikeō in Greek = to dwell (present tense)
21. I find then a law, that, when I would do good, evil is present with me.
'present' = parakeimai in Greek = 1) to lie beside, to be near
2) to be present, at hand
25. I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
'flesh' = sarx in Greek = the flesh, denotes mere human nature, the earthly nature of man apart from divine influence, and therefore prone to sin and opposed to God
'sin' = hamartia in Greek = to miss or wander from the path of uprightness and honour, to do or go wrong
