How to deal with dog anxiety?

I have a 2 year old toy poodle. She’s a very anxious and clingy dog. I’m a senior in college, living alone so I’m solely responsible for her. She often refuses to go to the bathroom when I need to leave, etc. getting in the way of my education, or hiding under furniture if I frown or cry, etc. I have both severe anxiety and depression, and I can’t work through my emotions because if I feel anything, even if I’m not outwardly showing it, she gets nervous or affected. Despite my mental health struggles, I do everything I’m supposed to for her, feeding/water, plenty of walks, enrichment, regular bathroom breaks, etc. I even find myself pretending not to be depressed and putting on a cheery mood so she won’t get upset. My family had thought that it was a better idea to get me a dog than a therapist so here I am. I love her more than anything and won’t get rid of her, but her anxiety makes mine worse. Is there any way to deal with an anxious dog while also having the space to take care of myself? What causes such bad anxiety in dogs?