How does pregnancy work

So I finally had sex with my boyfriend after waiting for an long while, I was one week away from my period start date so I felt it was safe to go raw. Well 4 days later still no period and I'm starting to be concerned because my period is like clock work it comes on the same day or within a day or two.

I took a test, it came back negative however, it has only been 2 weeks so I was wondering how does pregnancy work? Is it wayyyy too soon to know if I'm pregnant, Or should I know now? I have been stressed at work lately but I took a week vacation came back refreshed any thoughts because I dont k ow what to think.