The entire concept of Occupational Health is to find ways to allow you to partake in the course, not bar you from it. They might make recommendations for reasonable adjustments if they feel it necessary, for example the option of seeing a counselor while studying, or working specific hours etc.
With regards to mental health problems, they're quite common in the NHS, and most staff will at some point have suffered from stress or anxiety due to the nature of the profession. OH will probably just want to clarify that you know what you're letting yourself in for, and then find ways to implement a support network so that should the need arise, the help is already there to stop you from becoming ill yourself.
Depression, ED's, Suicide attempts, self harm, they're not a complete bar to the profession. If anything having had the experience in the past, might make you more valuable as you've got experience as a service user!
I know it's easier said than done, but try not to panic, it's not as scary as it seems.