no symptoms

on january 7th i had sex with my boyfriend , he claims that he pulled out, and i seen when he did , but i felt something inside, i don’t know if was me getting really wet, but my last period was on the 24th of december , and my periods don’t usually come on the same day each month because i’m in the house with my sister , aunt and my mom so our periods get thrown off all the time . i haven’t had any symptoms of me being pregnant , but i haven’t had my period yet and this month is almost over !? at this point i’ve been stressing/scared . i ran and got a pregnancy test from walgreens and that one came out negative . i then had my mom get me two more and they both came out negative as well . is it possible i can skip a month without a period , or am i keeping it from coming because i’m worried/stressing ?