<human>: Can you succinctly summarize the text in 1-3 sentences?

I'll keep this short because I posted here before, but my situation has gotten worse. Basically, a few days ago, randomly and completely out of the blue, I started to not feel like myself. 

While this includes a lack of motivation, and a overwhelming feeling of apathy toward things like school work, getting out of bed etc., I all of a sudden don't feel the same as I did toward my bf.

We broke up once in the past because his feelings for me dissipated quite rapidly, but we got back together a few months ago. For some reason, I randomly just feel completely empty and depressed. 

It's terrifying feeling like I may not have those feelings anymore...I talked to him about it and he understands, but our conversation sounded like we had already broken up.

I don't want to throw away a great relationship if this instance was the cause of something mental (i.e severe anxiety or possibly a new emergence of depression, etc). Has anyone out there had this happen? I'm terrified I'm going to make a choice in the wrong head space and regret it. And I'm terrified that I won't recognize this for what it really is, and ignore treatment if it's needed.
<bot>: I randomly feel completely apathetic toward everything, including my relationship. Does this ever happen to anyone else, and if it does, should I be more worried about something wrong in the relationship, or with my mental health?