I missed my period I'm only 15

that I could be pregnant I know I never had sex with him but I gave him head once with also my hand he helped to and then we cuddled for a bit he then fingered me but that was like 2 weeks ago. I missed my period and I was thinking what if he got some of his semen or precum on his finger left over but I have a semi irregular period but it comes usually at the end of the month but hasn't come im not sure if I need to be worried