How can I take care of my depression from a breakup?

Have you tried to allow yourself some breathing space to emotionally recuperate from the breakup?

Sometimes people expect themselves to bounce back faster than is feasible.  Then, the suffer from both the sadness and distractibility from the breakup in addition to the suffering which is self-induced by not permitting time to feel upset about the loss of the relationship.

Be gentle and kind toward yourself because loving yourself will release some of the tension you feel.

Since you write that you cannot function and you wrote a question on an online website, maybe you're not giving yourself enough credit for your capacity to function.

Anyone who is not functioning wouldn't be capable to write a question about themselves.

While what you write about yourself is in broad terms, my equally broad answer is you may be doing better than you think and the key problem is the discomfort and impatience that the feeling of sadness from the breakup, was more in the past than currently is the case.