Hi Melanie,
In the links I posted in your Introduction, there is a section on side effects. https://www.dietdoctor.com/low-carb#side-effects
Are you drinking salted boullion or adding salt? That is now included in the new Atkins plans. That helped me avoid fatigue, headache, etc....a cup of boullion Mid-morning and afternoon also replaced snacks and fixed any hunger. Also consider eliminating all artificial sweeteners, they can cause headaches and gastrointestinal upset. Unsure what 'feel horrible' is so check the list of side effects, many great tips to fix what ails you

There is a list of prescription drugs that slow weight loss by class here: https://forum.lowcarber.org/showthread.php?t=453311
Is your rejection drug a steroid? If so, my thoughts on slower weight loss posted in your intro apply. The person who helped me was Jackie Eberstein, Dr Atkins nurse for 30 years and now at Heal Clinic. She has seen weight loss patients on every drug out there. Her advice to me while on a hormone drug was eliminate nuts, wine and cheese. A clean, simple low carb diet is something to consider. Hope that helps.