hi peaches...
the song: association with sad feelings from your past/present
depression: avoidance behavior doesn't always work as much as we'd like it to.
falling apart when T was coming home: you had used useful techniques to keep a balance while your T was gone but, imho, you had felt vulnerable while she was gone and you knew it was finally safe to break down cause she was back.
keep in mmind, too, that you have a lot on your plate with taking care of your hubby. do u allow yourself some time just for you?
i hope you are feeling better now that your T is home. i believe you did an outstanding job of holding it together and using good coping skills even tho u felt vulnerable.