Am I pregnant? HELP!

OK so, I'm 21 and I've been in a relationship for 6 years. My bf and i are both regular weed smokers. So here's my dilemma. ..

Background: I use a period tracker app and I may have my cycle days listed wrong cause the app always predicts my period to be a few days earlier but is always arrives within a week of that. My last period going by the app was supposed to be on the 18th of February 2018 but it came on the 23rd of February. This was no shock.

On March 3rd/4th after a few months with no sex, my bf and I after a night out got carried away...

*** TMI Warning ***

We had vaginal sex but then my bf asked for anal and he had been begging for years for anal and I let him have it. I let him cum in my ass twice and afterwards he fingered my ass and as a result of alcohol he got carried away and started rubbing my vagina and then he inserted his finger 2/3 times but not all the way in ( then length of time it took me to realise STOP WHAT YOUR DOING 😂 )

My tracker app says my period was due for 18th of March but I know that that it is a few days off. But there's still no sign of my period. But I am slightly in denial and paranoid cause I just found out my 17yr old sister is pregnant.

I don't feel like I have any symptoms of early pregnancy, I don't have PMS either. But I do feel a lil something going on in that region.

I just dont know what to do, I need advice ?? Please help 🙈