To get OSAP I have to send the university a letter explaining why I was on academic probation (I'm on probation due to medical reasons and I wasn't satisfied with the program I was in). Has anyone done something like this? I am not sure about the structure of the letter (eg. how long it should be etc) and I'm concerned about what my chances of getting OSAP are now!! Do you think my situation will still have them accept my application and should I provide a doctor's note too, they didn't ask for one but in case they do later? I'm going to go to campus later and talk with them in person too but I still need help with how the letter is to be written.

The letter should be a page long specifying why you were placed on academic probation and also provide medical documentation for proof of the medical reasons you specified. You should also make mention of any improvements you have noticed regarding your reasons and grades and what you plan on doing to improve your studies. As long as you mention all that, I see no reason as I why they wouldn't accept your application. They'd just like to know why you were placed on probation in the first place.

This takes a lot of stress off me! thank you so much!!

No problem, don't stress out too much and just write it to the best of your ability with all the relevant information.