pregnant?

me and my SO have had protected sex a few times, but one of the days he had pushed it in like maybe 1/3 the way without anything on before we did anything. this app said i was ovulating that day with 11% chance of pregnancy. i’ve done two tests that both said not pregnant, but my period was supposed to come on the 24th, and it still hasn’t come. i’m only 17 and my periods have been pretty irregular before (like have gone a couple months without it before) that last two months they were regular though and i’m just worried! what do y’all think?