Am I pregnant ???

I am 20 years old and have never had an extremely irregular period. There have been instances where I’ve started a few days later or earlier than expected, but that’s usually happened because the women I was living with/hanging around enough pulled me close to their cycle.

I have not had a period since December of 2017 (19th-22nd).

I’ve taken two pregnancy tests at varying points, the most recent being within this last week, and both have come out negative.

I’ve relentlessly searched the web for ways to differentiate between an irregular period and pregnancy, but everything contradicts one another and I’m more confused now than I was when I began.

Can I still be pregnant even if 2 pregnancy tests read as negative? (Different brands and about two weeks in between tests)

If I’m not pregnant then what on earth could be causing me to completely miss a period?

I’ve never tracked my periods before and, ironically enough, downloaded this app during my last period so I could start keeping track but now have no period to keep track of 🙃

My last period should have started around the 20th of January and if I make it a little over a week without a period still, I’ll have missed twice.

HELP