So heres how it is

My girlfriend is scared, because Her period has not arrived

She has irregular periods.  From since she started about them, their duration has been 28, 31, 29, 33 so on.

She is on day 33 today, and it has not arrived.  Our last sexual activity was Thursday the 1st of April.  There was no intercourse.  She gave me manual sex and I gave her oral sex. The manual sex was done through my boxers, and during ejaction, the semen seeped through the boxer shorts, altough i'm fairly sure neither her or I touched it. We continued to muck around, and my fingers did go around the otside of her vagina, but there was no penetration. Only around the around the legs, just above her clitoris and on her underwear.  There was not any noticable semen on my hands, i had been moving my hands along the bed as well, and im fairly sure my hands were dry.

Earlier that day (Like an hour, hour and a bit)  I was mixing pool salt in our pool with my hands.  I also washed my hands before we had done anything.  And im fairly sure i had gone to the toilet and washed my hands before we started mucking around again.

She wants to know if there is a chance she could be pregenant.  She is concerened as her period has not arrived yet, although lately, she has been eating unhealthy, been stressed by her studies and was on an antibiotic for the monday through to the wednsday night thursday morning.  These would all contribute to the timing of her period yes?

Thank you for your time.