How did I get pregnant so easily?

If he ejaculated anywhere near your vagina, then thats the likely cause.

Sperm cells are very very fast swimmers practically by the time a guy ejaculates they could be up in the fallopian tube already fertilizing an egg.

To be honest, what happened to you was like 1 in 1000 chance, but guess what it happened. Its not really about being pregnant easily its just that the sperm cells knew were exactly to go, most sperm cells travel in the wrong direction so I’m guessing he had some smart as hell sperm cells. (thats a joke by the way :) )

This is actually a perfect example of what can happen when a girl is anywhere near a man’s ejaculation, this can happen to anyone and I’m pretty sure you can teach people to be protected because the chance of this happening is likely ;)

At least you learned your lesson, or so I think you did. If you don’t want that happening again, use a condom or be at a safe distance from a man when he is about to ejaculate.