Is the so called hook effect real? ive read about testing negative for pregnancy only cause there is too much hcg, that disturba the pregnancy test?

That's theoretical.: In real life, a urine test gives a reliable result by 3 weeks after sex (3 weeks after when conception might have occurred) or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant, and a test is not needed.