I had sex on 17th feb and still havent got my periods my date was 9 march and my pregnancy test is coming negative i dont know why?

Some normal women occasionally skip a cycle for no apparent reason. If the absence of menses continues for more than 60-90 days your doc may offer hormonal pills to bring on a cycle. (if your pregnancy test remains negative.) Pregnancy teats can be falsely negative early in the process. A first morning urine is considered the most concentrated for pregnancy hormones. Re=testing may show positive.