just making sure

Do I know a uni has finally accepted me when I have received my accommodation? I just received my housing letter. I'm just overthinking like what if I get there and say I haven't done the process correctly

You know your university has accepted you when UCAS says "Congratulations - you've been placed at your firm/insurance choice [university or college] to study [course]!".
If you're talking about the processes from thereon (securing accomodation, enrolling, etc.) then there's no guaranteed way to be sure that you've done that entirely correctly.

uh oh I haven't gotten the congrats email, I accepted them on UCAS on the 15th but I havent got a congrats email... what should I do?

I was referring to your status in UCAS Hub, not an e-mail.
The fact that you say that you accepted them on the 15th sounds like you might have applied via Clearing. Is that right? In that case, you should have a message looking something like this in UCAS Hub:

Do you? If not, what does UCAS Hub say your status is?

Oh yes I have that! Okay phew, I was thinking that I needed an email that also said it. I'm sorry for the trouble