If you have a 28 days cycle, it is not possible to be pregnant 5 days prior to mensis.

Probably not. It is possible to be pregnant 5 days before but if you took a pregnancy test that was negative after your period, 19 March, you are not pregnant.

You really have to wait until you are late for your period to see, if your next period doesn’t come when expected- then take a pregnancy test. That’s the only time you can be sure with a negative test that you are not pregnant. Or see your physician for a blood test when you miss a period.

Pregnancy test is usually positive 2 weeks after ovulation or 4 weeks from the first day of your last period(only if you a 28 day cycle)
In most women ovulation days vary depending on the length of the cycle, hence the time when pregnant test is positive also varies.
Repeat your pregnancy test in 1 week again if you do not have a period. If you are still concerned, see your OBGyn.
Good luck and stay healthy!

March 12 is little late for ovulation if you’re getting regular menses however l would be careful and repeat pregnancy test ln one more week