How long does your Doctor recommend you take off? Does he have to send in a
full medical report to your employer? When does your sick-leave begin? I do not think it will affect your future as you could discuss your illness being related to a single one-off incident with future employers. Have you talked to your Doctor about your fears regarding what is written on your medical report as this is not helping your stress condition I'm sure. I understand why this would be a concern but don't you just need to take care of yourself now and leave the future to sort itself out.
However, before you go on sick leave maybe you could -
- ask your Doctor to write up your illness in his medical notes in a way which will limit damage to future employment
- Get a full written reference from your employer now and make up the reason as to why you need it