Doing school work that doesn’t give you any pleasure can produce a lot of anxiety, particularly when you don’t have as much of the usual social supports that helped you in the past. This time of Covid is making everyone everywhere feel weird and out of sorts.
I assume that you text and have video chats with your girlfriend now and then. Have you thought about adopting another dog? Is there something that does make you feel relaxed and happy? Like watching a comedy movie, researching something on the internet unrelated to schoolwork, baking a treat, or running or biking? If there is, you could alternate doing your coursework with something that makes you feel better to stay on an even keel.