Any idea???

So my period in July was 26 days late. At the time I hadn't had sex in over a year 1/2. My cycle ended on August 1. On August 3 me and then this guy didn't exactly have sex because all he did was put the condom on slipped and in and we both agreed it was weird and he left. Maybe like 1 minute of being in me and that was it. However August 7th I slept with this other guy (DONT JUDGE ME) and we used protection. We've been having sex for a little over a month. My period is 16 days late and he thinks nothing of it. Maybe it's stress?? Or maybe it's just nothing. I'm trying hard not to think about it and using the time I'm given to get laid. However, maybe it's because I haven't had sex in awhile that its just late...