How do I focus on studying for nursing school when my SO pisses me off?

Backstory: I was in nursing school before and I had to drop out. I told everyone it was because my bills were killing me and I had to go back to work. That is only half the truth. The majority of it was that I felt like I had no support. My sO was more worried about me spending time with him and made me feel like shit when I didn't.

Now: I'm back in nursing school. My SO has had mystery health problems for about 3 years and he is such a big freakin baby. He gets mad and throws stuff and yells at us and slams doors because he isn't feeling well and the hundreds of test the dr's have done resulted in nothing. I'm worried that his child-like tantrums are gonna distract me from getting done what I need to again. Any advice?