My sender email is set to my own email, so whenever I get a new order, I get notified with an email from my own email address. However, this email always ends up in junk.
I don't have my own domain, I use outlook.live.com, so I can't edit the SPF records. I have tried adding my own email to the safe mailing list and creating rules that move my emails from junk to inbox but nothing has worked.
The weird thing is if I send an email to myself it goes to inbox so I'm not sure why the shopify emails from me end up in my junk.
Any help would be appreciated.
I think you'll struggle here. It is likely that Microsoft will always deem these messages as spam. The problem when you use a domain you can't control, as you mention, is that you can't add any kind of authentication. In these cases, Shopify will automatically send using their own return-path (shopifyemail.com) and similarly will sign with shopifyemail.com. Although SPF and DKIM will pass, they will not align with your domain and will therefore fail DMARC.
Your best bet really is to get yourself a cheap domain name that you can control.