Romans 7 goes on to explain who Paul "was" and not, "who he is" we know this because from Romans 7:7 onward Paul is telling us who he "was" without Christ and not who he "is" in Christ. The beginning verses of Romans 7 Paul uses the law of divorce and remarriage to show you have to be dead to one before you can marry another. Sin has to be dead in your life before you can marry Christ Jesus in the spiritual. Christanity are walking around as adulterers still married to the devil to their sin while proclaiming to be married to Christ. Married in their darkness of sin while claiming to be married to the light. Bastard children of the devil It doesn't work that way can't have light and darkness at the same time. Can't serve two masters, can't serve the devil sin and Jesus righteousness at the sametime.
Paul for 33 times uses the letter, "I" to show you that if you are in his shoes stuck in sin you are in a mess. Paul finally ends his message that he was a wretched old man in his sin. When you are in Romans 7: 7-24 stuck in your sin, you are a wretched old man. Paul leads us out of this by saying he serves the law of sin. Paul is not breaking the law he serves the law if Paul broke the law then he would be a sinner. If I walk by my neighbour's house and mind my own business I am serving the law not breaking it. If I threw rocks and stones at my neighbor's front window or car then I am now breaking the law. Paul takes us out of all this in Romans 8:1 and takes us from the "then" to the "Now"
Romans 7 :14 Paul is telling us that the law is spiritual, but he was dead in his sin so he would have been carnal dead in his sin and trespasses. This is what it is today Christians who are still carnal dead in their sin and trespasses have no clue what the spiritual is saying. Verse 15-18 Paul is telling us the motions of sin he was going through. It goes back to Genesis 4:7. No good thing dwelt in me as a sinner, I cheated, lied, stole, gambled etc. Man will pierce their ears and belly and do all sorts of things beyond their wild imagination because of their sin. Look at the mess the whole world is in right now because of sin.
Paul is talking about the law the ten commandments what Moses had the law of sin and death. Jesus came with a new law the law of the spirit of life in Christ Jesus. Romans 8:1-2.
Romans 7: Know ye not, brethren, (for I speak to them that know the law,) how that the law hath dominion over a man as long as he liveth?  For the woman which hath an husband is bound by the law to her husband so long as he liveth; but if the husband be dead, she is loosed from the law of her husband.
 So then if, while her husband liveth, she be married to another man, she shall be called an adulteress: but if her husband be dead, she is free from that law; so that she is no adulteress, though she be married to another man.
 Wherefore, my brethren, ye also are become dead to the law by the body of Christ; that ye should be married to another, even to him who is raised from the dead, that we should bring forth fruit unto God.  For ---》when we were《---- in the flesh, the motions of sins, which were by the law, did work in our members to bring forth fruit unto death.  But ---》now《--- we are delivered from the law, that being dead wherein we were held; that we should serve in newness of spirit, and not in the oldness of the letter.  What shall we say then? Is the law sin? God forbid. Nay, I ---》had not《--- known sin, but by the law: for I ---》had not《--- known lust, except the law had said, Thou shalt not covet. 8] But sin, taking occasion by the commandment, wrought in me all manner of concupiscence. For without the law sin was dead.  For --》I was 《---alive without the law once: but when the commandment came, sin revived, and I died.
 For we know that the law is spiritual: but I am carnal, sold under sin.  For that which I do I allow not: for what I would, that do I not; but what I hate, that do I.  If then I do that which I would not, I consent unto the law that it is good.  Now then it is no more I that do it, but sin that dwelleth in me.  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.  For the good that I would I do not: but the evil which I would not, that I do.  Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
Genesis 4: If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him.
Romans 8:1] There is therefore--》 now 《---no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.  For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.