What was one external conflict Charlie Gordon had in the book?

In harmony with the above comments, Charlie struggled with fitting in: when he lacked intelligence he always allowed things to happen to himself in order to amuse Joe, Frank, et al and as his intelligence increased he had trouble fitting in with those who weren't as smart as he had become especially Ms. Kinnian because he would talk about concertos, math, and many languages and those less intelligent people were unable to comprehend. So on both ends of the spectrum Charlie struggled with acceptance.