How can I see my doctor sooner than my appointment (very urgent issue)?

About 2 months ago I was diagnosed with Hasimotos Thyroiditis (mine was HypERthyroidism, not hypo), and I've been prescribed Carbimazole tablets to take. My doctor recently told me to increase my medication to 4 tablets a day, and a few days ago I noticed an ulcer on the left hand side of my mouth. The next day, I had another ulcer on the right hand side. They're not really sore anymore, but I can still feel them. As well as this, I've had a sore throat and a burning sensation when I use the bathroom. My doctor told me this is rare, but if it happens, to see her immediately so I can stop the medication and go to hospital to have a full blood test count. I made an appointment and I can't get in till this coming Thursday, exactly a week after my first ulcer appeared. I need to go in a lot sooner than this, as you can in fact die from it if you don't receive immediate medical attention. They couldn't book me in any sooner, even though I stressed how urgent my situation is. What can I do? My family is very worried, I've stopped taking the medication for now to be on the safe side, but is there any other way I can see my doctor immediately?