My menstrual period has always been on time. It would always come the end of a month to the beginning of the new month. I got my period January 2-7, then had gotten again 17-22 but it was more dark brown to black, and I thought its okay just left over blood. Then it came again February 1-6, started dark brown and ended dark red. Once more it came February 20-24 regular heavy blood flow. Now that is the end of march I have not receive it. Is this normal or What's going on? ( I had sex during these months) 19 years old

Could be normal, maybe not. You had sex and may be pregnant. You could just be late. Unprotected sex?

I wouldn't attribute this to pregnancy, I also wouldn't call it normal.

That said, it may be nothing to worry about, but I recommend talking to your doctor to get to the bottom of things.

Any time you have sex, even with protection, pregnancy is possible.

It sounds like you're having an off month, which can happen for many different reasons, stress, medication, illness, weight gain, weight loss, etc. etc. But pregnancy is also possible.

Since you had an off month last month, I'd wait another week. If you don't get your period then, I'd try a pregnancy test. If that test is negative, wait and see what happens next month. If you miss another period then test again or get a blood test done.