What Causes Itchy Rashes And Sores Around Chest And Neck?

I m a 50 year-old female, recently stopped taking Sertraline hcl 50 mg (about a week and a half ago) because of the development of an itchy rash with sores that bled on my neck and chest. Started taking this med over the summer to relieve hot flashes and noticed the rash shortly after, didn t do anything about it right away. Finally went to a dermatologist, he did a biopsy and confirmed it was caused by something I ingested. This med is the new addition to my diet - figured I would stop taking it immediately to rid myself of the rash. Rash is still there but not quite as bad as when I was still on the med. For the past several days I ve been feeling light headed with a dull throbbing headache with bouts of nausea. Also since I started taking this med (in August) I ve had a weight gain. No matter what I do, it s sticking with me. I go to the gym 2-3 times a week (try to get 3 miles in 30 min on the ellyptical) and have been watching my diet. I m a non-smoker, general health is good but lately I just don t feel like myself. Not that it s likely but I ll confirm that I m not pregnant. Thoughts?