Stress can definitely cause health issues, and it sounds like you’re under a lot of stress right now.
It’s important to realize that individuals with ADHD mature at a much slower rate. While she’s nearly 21, developmentally, she’s more like 18.
I would sit down with her and draw up a contract between the two of you, spelling out what each of you can expect from the other. Explain that you’re happy to help her out and allow her to continue to live at home, but that she has to meet you half way. List what she gets from you (cell phone, roof over her head, support, help with baby, etc) and list what you will get from her (specific weekly chores, a respectful attitude, help when you need it, continued employment, etc.). Then, spell out the consequences if expectations aren’t met. Both of you will sign it and display it on the refrigerator or something. Writing it up in this way can make a huge difference.
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism