I know I may sound extremely paranoid, but I still want to ask so as to put my heart at ease.

My boyfriend and I were fooling around and he rubbed his penis to my vulva. I'm positive he didn't ejaculate earlier in the day, and, also, he didn't ejaculate or penetrate while we were fooling around. The day after, I started my normally heavy period. I'm not entirely sure if he was excreting pre-cum or not, and my period lasted for about 6 days, starting with brown discharge and progressing into clumpy deep red blood and ending again with brown discharge.

Is there a chance of me being pregnant? (also, if this isn't asking to much, a percentage would be nice--please)

Thanks so much for reading and answering.