Mac is constantly disconnecting from wifi?
So I bought a 13" mac book pro four days ago and it's been disconnecting from the internet about once every 2-10 minutes. It freezes constantly and pin wheels frequently for long periods of time when I have two or three things open. My iPhone hasn't lost connection with the wifi either, because when my mac disconnects my iPhone (running only on wifi) has no problem. This is the first mac I have ever bought and I am really frustrated because I have no idea what the issue is.
Also, how do I keep my photos from uploading to my mac? I deleted all of the pictures, but they keep uploading instantly. Is there a way to stop iCloud from uploading without deleting my entire photo stream in my phone? Even when I delete them (on my mac) and delete the recently deleted it still shows something like 2 gigs of photos on my mac hard drive.
Sorry in advanced if these are all silly questions; i'm new.
MacBook Pro with Retina display, version 10.11.13