Then after fourteen years I went up again to Jerusalem with Barnabas, taking Titus along with me.  I went up because of a revelation and set before them (though privately before those who seemed influential) the gospel that I proclaim among the Gentiles, in order to make sure I was not running or had not run in vain.
Paul met with influential leaders about this false doctrine that was being preached. If the other apostles did not confirm his message and renounce the false teachers, it would be very hard for him to retain his converts. These false teachers were telling the new converts that Paul’s message was not doctrine. Paul knew his message was God-revealed and therefore true. Paul would not be able to keep his churches in sound gospel teaching if he could not disprove this false teaching. This is why Paul said he was in fear of running his race in vain.