Feeling like a fraud isn’t evidence. Look at the actual record: you got here, and you did the work.

That feeling turns up most in people who are stretching, because it is produced by being somewhere new rather than by being unqualified. It has no access to your results at all. It only reports that things feel unfamiliar, then invites you to read that as a verdict on whether you belong.

Keep a plain file of what you have actually done. Grades, finished pieces, times someone asked for your help, problems you sorted out. Read it when the feeling arrives. Facts are slow and boring and they win the argument.