@jmb73 - Welcome to Mayo Clinic Connect!
First thing to focus on is the nodule in your neck. You will have the ultrasound soon. Even if your PC went on maternity leave, she has someone who helps take care of her patients. The office staff knows and you should be able to talk to that doctor. You have an endocrinologist as well.
It is hard to lose weight when your hormones are unstable.
Also, if you continue on a 900 cal diet, the body will think it’s in starvation mode and you won’t lose weight because of that.
You have and have had multiple medical problems- it is overwhelming at times. I just think that you have to find out what the neck lump is as soon as possible.
Please correct me if I interpreted your wrong main concern.