Welcome to Healing Well.
I am sorry that you are in such a bad spot right now, but I have to agree with gettingby, sometimes you just have to let someone go and move on.
IMHO she is using you for a conveince when she needs someone to take care of her. You need to set boundaries, IMHO, and stick to them. There must be someone else she can call on if she needs favors.
Please follow up with your Pdoc and continue your medication. The AD meds will take up to 4-6 weeks to kick in. Therapy to help you work on your self esteem would be something you may need to move forward.
Please take care of you and keep on posting here. There are many caring people here.
I agree as well. I dont think there is much that I can really say that has not already been said, but it definately sounds like it is time to let go as you risk running yourself into the ground and making yourself ill as well. Are you able to take a vacation? Perhaps changing your phone number might be a good idea if it is a problem when she keeps ringing you.
Keep your head up, and your eyes open.