Am i late for registering for classes?

I still dont have an advisor and didnt attend NSO due to medical reasons and im not in the US. Im gonna major in human biology, pre med. Ofcourse im so lost and everything seems so scary, new, and confusing. It feels like everyone knows what they’re doing except me 😭 what makes it worse is that im a first gen. Idk what to do. Genuinely. Im gonna be back in the US next month. How do i even register for classes or do anything?? Im just scared that im late for registration and the classes are full.