If I am still preaching: This likely refers to Paul's preaching as an enthusiastic supporter of Judaism before he converted to Christianity (1:13–14; Acts 7:58–8:3). As a Christian, Paul never preached that non-Jews must be circumcised.
Why am I still being persecuted? If Paul had been promoting a religion based on laws, the devoted Jews would not have been persecuting him everywhere he went. These leaders were angry because Paul taught that people did not need to follow the law of Moses to be saved. They thought this teaching was deeply offensive (compare Romans 9:33; 1 Corinthians 1:23).