No IP Address/Self Assigned IP Help?!

Alas, I have to resort to making my own post about this issue because everything I have tried, has failed.

So, I shut down my macbook for the first time in a long time on Saturday morning. When I came back on Sunday evening, I turned on my macbook and found that it wasn't connecting to the Wi-Fi at all. It kept giving me connection timeout issues along with my Wi-Fi symbol having a little exclamation point in it, so I went into system preferences -> network to see if it would tell me more and up came the "no IP address" message. So after millions of attempts to troubleshoot myself, i asked my sister to take a look and she renewed the DHCP Lease. This worked, but only for a while, as soon as my macbook went to sleep, it disconnected again. So I tried renewing it again, but it wasn't working and by probably 14th attempt, it finally worked. Again, it only lasted a while.

I finally began looking up what to do online and had a look at what others did. I removed my network and added it again, nope, moved it to the top of preferred networks, nope, removed the wi-fi all together, nope. Then I tried manually entering my IP address, this worked but much like the DHCP lease, it didn't last long and also caused my sister to have the issues I'm currently having with her macbook. This is when we both began getting the "self-assigned IP" message. I did read something about macbook's stealing IP's from each other but I'm not too sure about that as I didn't look into it much. So then I tried the PRAM reset aswell but no luck. Of course I have restarted both my macbook and my router to see if this fixed the issue but nope. Everyone else, and my sister before I manually entered the IP address, can connect to our Wi-Fi perfectly fine. I've used this Macbook and the Wi-Fi perfectly fine for an entire year, and my sister used it 2 years before that perfectly fine. This issue has only raised since I turned my Macbook off. I can connect to my Wi-Fi using some of the solutions above, but it is a real luck and chance game because it takes lots and lots of attempts before it works and it is extremely frustrating.

So to summarise, ever since I have turned my macbook off, my macbook has struggled to connect to our Wi-Fi. I have tried almost every solution I can find which only sometimes work, and work for a brief amount of time. Every time my Macbook goes to sleep, it will disconnect. I am now needing your advice!

Thank you!