What Causes Stoppage In Menstruation?

my boyfriend and i were fooling around and he fingered my ass awhile after he came (we made lunch, ate lunch, talked for awhile then he fingered me. It was all in about a half hour), his hand was dry too. Then the next day he jacked with his penis inside his pajamas and his hand outside then fingered me before he came then much later after he washed his hands (he said) then he ate me out but never fingered me (cause i wouldnt let him) and then i jacked him off and put a little pre-cum in his mouth. I know that when semen is dry the sperm is dead, and i know sperm cant travel through clothing and I know salvia is acidic and would kill sperm. But I sill havent gotten me period and i am 5 days late. Could i just be stressing? I have taken 3 HPTs and all have been negative. I took one before my missed period, one the day of my missed period and one 2 days after with First Morning Urine. I'm thinking of taking one on Wednesday (it will be one week late if i dont get it) and if i still dont get it, I might get a blood test.

But could I be pregnant?