Confusion

So I've heard a lot of different things about if pregnancy from precum can happen or not. A lot of people say no and others say yes. Is there a reliable source that anyone knows of that can point me in the right direction?

I've done some stuff with a guy and he got his precum on his fingers without realizing it and he rubbed me a little bit. He didn't finger me or anything. (This was on January 14) My period is now 3 days late and it's starting to worry me. I feel like I'm over reacting but at the same time what if? I've been under a lot of stress lately so I know it definitely can also be that. But I've also been having minimum, way less painful than my normal cramps, cramps. Any advice?

Update: my period started today