Could i be pregnant?

My boyfriend and i decided to do ..instead of l, because well thats the closest i will let him get because i would rather wait until im married for my virginity to be taken..ANYways..He shot on my back..and a little of it kind of got on my leg. i wasnt expecting this and it was really close to my l area..i know sperm can travel along bodily fluids. but i just recently have started my period the thing is its lighter than usual. ive heard this could be a sign.