I am also an older woman. I've been diagnosed with major depression for a long time and recently they switched the diagnosis to Bipolar 2. I understand the depression phase really well. I am so sorry you have been going through all of this. It is scary and when I know I am slipping down, sometimes I feel like the cartoon images of the coyote holding on after the roadrunner ran over him. I just know I'm not going to make it.
But the truth is that there always is an end to the tunnel even when I can't see it. You've been through a lot in the last few months. You don't say how long ago the last med change was but some of the meds can take up to 4 weeks to be fully effective depending on what they are.
I wish you luck with the therapist and doctor appts. Use your support system. Best wishes.