I don't know if it's possible for me to be pregnant?

I was hooking up with a guy (giving head) when he tried to have with me, I wasn't for it so I told him to stop but I think our privates made contact. I'm now a week late on my period and show no signs of pregnancy except my urine is bright yellow but I did begin taking a new multi-vitamin. If the contact was only for a few seconds and he didn't ACTUALLY go inside of me, what are the chances of me being pregnant? I'm freaking out, I've never been this late for my period. I'm experiencing minor cramps right now as if I may be getting it but I'm still worried sick I could be pregnant although writing this has made me believe I'm not. Someone help, maybe with a statistic about pregnancys without ? IM SO SCARED.