No, title IX is not a constitutional amendment.
Title IX of the Education Amendments of 1972 is a
US law (which was passed into law on June 23, 1972), which was later renamed in 2002 as the Patsy T Mink Equal Opportunity in Education Act, but is most commonly known simply as Title IX.
The law states that
No person in the United States shall, on the basis of sex, be excluded from participation in, be denied the benefits of, or be subjected to discrimination under any education program or activity receiving Federal financial assistance...
-United States Code Section 20.
Although Title IX is best known for its impact on high school and collegiate athletics, the original statute made no explicit mention of sports.