Pregnant?

Hi everyone. I was wondering how soon after you technically “become pregnant” you can tell from the pee tests. I had unprotected sex a few times with my boyfriend in last few weeks. I was supposed to get my period a few days ago but havent(it’s not always spot on though) but I’ve been super tired, nauseous sometimes and I just have a weird feeling but I was y sure if I’d even have symptoms if it just happened maybe at most two weeks ago. Thanks :)