my boyfriend ejaculated onto my stomache, he then used tissues to wipe it of,but not sure if he got every single bit of sperm , i then took a shower immediatly after, could i be pregnant from this? (what im worried over is the shower water washing any left over sperm into my vagina?, i was obivously standing up in the shower, and most of the sperm had already been wiped of, if there was any left)