First of all I hope you are doing better. Spinal surgery is serious buisness.
As for your letter this is important. You have not given all the information to the visa officials and this could be pretty serious. Your best best is to write a letter, including photocopies of ALL the medical records and documentation that is important and send it ASAP. What you can do is reference the photocopies in your letter.You might even concider calling. (I don't know how serious this is).
Here are a couple suggestions to get you started. Try to write the letter and then post it again so we can try to help you more.
**THIS IS JUST AN EXAMPLE...YOU NEED TO PERSONALIZE IT AND MAKE IT CORRECT!** don't jsut copy and paste!!!!
To whom it may concern,
I regret to inform you that I have failed to comply with the rules set out by __________ (the home office or visa agency). I applied for my visa when I was working towards ____degree at -----university. After paying all my fees and registring with that university, ------university closed down.
As a result I enrolled in ------ Universty program...DATE. I was not aware that I should have informed the home office of this change at that time. I have been informed of this requirement and this is the purpose of this letter.
I reget to inform you that this occured twice more, due to serious illness (STATE ILLNESS HERE). (Explain what happened, like you did here in the forum...be direct and honest.)
I would also like to take this opportunity to clarify why there was a gap of ----(time) between my studies. This also was due to my (state illness). Due to **(number) of spinal surgeries and long recover periods I was unable to enroll and study.
My visa has expired (give date and info) and (tell them what you want to do...do you want to renew it? etc)
My appologies for not providing this information at the correct moment.
Please see attached medical records for more details.
Thank you for your understanding
Please remember that this is just an example and is NOT complete. I would feel aweful if you copied and pasted it and sent it. You need to add information and change it to suit your situation. OK!!!
Best of luck!
LEARN ENGLISH BY USING IT: ANSWERS & MOTIVATION FOR ANY ENGLISH LEARNER