So I sort of had sex with my boyfriend about a month ago now (we just tried to see how it goes in lol) and he didn't cum or anything but he says he can't be sure (is that even possible?).

And now my periods are late by 15 whole days! I took a pregnancy test (the strips thing) like twice, and they were both negative.

Are they wrong or are my hormones suddenly messing with me?

My periods are usually kind of irregular, never on time by about 5 days or so. But 15days?! Im so scared even though the tests I took were negative