Let's analyse the passage:
"I go on to visions and revelations from the Lord"
Paul is introducing the topic that he is now going to discuss.
"I know a man in Christ who fourteen years ago was caught up to the third heaven. Whether it was in the body or out of the body I do not know--God knows."
He is saying here that he knows a man who was caught up to the third heaven. He didn't know how it happened. If it was actually Paul, he would have known whether in the body or out of the body. The literal interpretation of this is that he is speaking of someone he knows who has related the vision to him. There is no indication at this stage that he is talking about himself. There is no sub-text to Paul's writing in general. He says what he means and means what he says, so we can trust that what he is saying is what we are reading, and not some "between the lines" inference that he is talking about himself.
"And I know that this man--whether in the body or apart from the body I do not know, but God knows--was caught up to paradise and heard inexpressible things, things that no one is permitted to tell."
Paul goes on with the description of the man's vision. He is still referring to someone other than himself.
Now here is a key verse that we should not ignore:
"I will boast about a man like that, but I will not boast about myself, except about my weaknesses."
Paul is saying that he will boast about a man who has visions like that, but he will not boast about himself, rather he will make a big deal about his own weaknesses. He does that when he talks of the shipwrecks, hunger, stonings and other persecutions that he had to cope with. Right at the start of the book he said that he was so hard pressed in Asia that he despaired of life. This verse clearly tells us that Paul was not speaking of himself when he described the man who had the visions. The problem is that people read into the Scripture what they want to see instead of what is actually there.
"Even if I should choose to boast, I would not be a fool, because I would be speaking the truth. But I refrain, so no one will think more of me than is warranted by what I do or say,"
This is telling us that Paul is actually not boasting at all, because he says that if he chose to boast, he would be telling the truth, but he is refraining from boasting so that people won't think of him more than the person he actually is. To say that Paul is making some sort of underhanded boasting statement about having a vision and downplaying it because of some supposed humility to making Paul out to be deceptive and therefore untrustworthy. If that is so, we have to cut out all of Paul's letters from our Bibles because we cannot depend on him telling the truth anywhere. I would rather believe that the theory that Paul was talking about himself about some sort of vision he had is a load of codswollop thought up by some silly dream from a person who is comprehension challenged, than to believe that all of Paul's writing is untrustworthy. I was a teacher of reading to young students, and I taught comprehension. I would say that those young students were more competent at basic comprehension than the people who are saying that Paul is talking about himself when describing the man with the vision.
"or because of these surpassingly great revelations. Therefore, in order to keep me from becoming conceited, I was given a thorn in my flesh, a messenger of Satan, to torment me."
Paul does not say that these revelations were actually given to him. He is still referring to the other person who received the revelations. Instead of great revelations, the Lord has given Paul a thorn in the flesh to keep him humble and remind him that there is no good in him and his only claim to fame is what Jesus did on the cross for him and His mercy in revealing Himself to Paul on the Damascus Road.
"Three times I pleaded with the Lord to take it way, but He said to me, “My grace is sufficient for you, for My power is perfected in weakness.” Therefore I will boast all the more gladly in my weaknesses, so that the power of Christ may rest on me."
So, instead of using the other man's revelations to spur him on to boasting about revelations that he might have had, he chooses not to follow the other man's examples but to boast about his weaknesses instead.
There is no way that anyone can interpret the passage any other way than what Paul literally wrote. Bible scholars, and I don't care how eminent or qualified they are, are in error and are misleading their readers if they say that Paul is talking about himself.