Good luck with the vet visit -- that's clearly the place to start.
Please also visit your own therapist. Crying for hours every day, and anxiety so bad you feel you can't come in to work, is a disproportionate response to your dog going through a rough patch. Sounds like an excellent time for a checkup -- after all, you need to take care of yourself at least as well as you take care of your dog.
Hugs and good luck.
Completely agree. There are two issues here: the dog, and the crying for hours in reaction to the dog.
1. The Dog. Echoing comments that a vet visit is in order.
Also, long story that might be helpful to you. I got a 5 year-old pound dog about a year ago. She had bad separation anxiety and it basically ran my life for a while. It was rough. She's also reactive (both to dogs and people) so daycare wasn't an option. You have my sympathies. It's so hard to feel trapped by your pet. I was working from home, and don't know what I would have done if I weren't.
I ended up following the method outlined in Julie Naismith's book Be Right Back (I listened to it for free using an Audible trial, and she also has a free Facebook group with some good info). Basically, I left the house for tiny periods of time, sans the normal "departure cues" like picking up keys, putting on a coat, starting the car, etc., and worked up to longer absences. I set up a camera situation (I would do a Facetime link between my iphone and ipad, and set the ipad where I could see her) to monitor her and make sure I returned immediately if she started to panic. And I set up a spreadsheet to track variables: length of absence, time of day, her reactions while I was gone, whether I had left a podcast on or not, etc. Once she could go for 40 minutes on her own, I introduced more departure cues, including driving away in the car. I also explained the issue to the vet, and got her a Prozac prescription. I took her in the car with me whenever I could since she seemed to do better in the car (obviously this is weather dependent). It took a while, and progress was not linear (yes, my spreadsheet did include a graph with a trendline), but she did get better, and my life is much better now too.
2. You. Since you have bipolar disorder and are crying for hours every day, a doctor visit also seems in order. I think it would be completely fair to describe the issue and your mental state to a doctor, and see if you could get a remote work accommodation at least temporarily, because of your mental health.