Most likely, you arent pregnant only paranoid. the same thing happened to me... Be carefule because there is sperm in precum, but he has to make it inside of your vagina in order for the sperm to do anything... just play it safe and always use condoms.
Hi,
If he accidentally ejaculated around/on your vulva; yes, there's a very slim possibility. Usually nausea, tender breasts, fatigue, and cramping in the first few weeks can be an indication of pregnancy; some women show signs earlier than others. The only way to find out if you are pregnant or not, would be to take a pregnancy test...
Good Luck