I've been in my job 17 months my team colleague left six months ago. I took on 30 percent of his work until a replacement was found. December was horrendous and on New Year's Eve I emailed my boss and said long term the workload was not sustainable and I found it too stressful. We took on someone in January but he has slow keyboard skills and has no capacity to take back the additional work. Leaving me doing six days work in 5. I can't do it anymore. I'm coming home with chest pains. I want to go on sick leave due to stress and Fife notice a week later ergo not sending a notice period. Is this acceptable?