Negative ovulation test had unprotected sex 7 days dpo sept 11th period was supposed to come before the 20th should i take a pregnancy test?

Yes. Ovulation tests may or may not be valid. Any unprotected intercourse can result in pregnancy. Some women occasionally skip a cycle. If it matters, test.

Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.