If you are a Marine at either Cherry Point or JAX, it's quite likely that this time they may decide to give you a court-martial; either a summary with administrative discharge, or a special.
The fact of the deployment is going to be considered an aggravating matter against you, especially if that meant you did not leave with and have not left to deploy.
I've seen anywhere from 30-90 days confinement and a BCD, for missing movement and UA such as this. There may be some negotiating room because of any special circumstances. That means you really have to get detailed information and documentation about the reasons for the absence to prove the medical issues. You'd have to at least explore the issue of medical necessity as mitigation or extenuation.
www.court-martial.com; www.court-martial.us.com; firstname.lastname@example.org 703-298-9562, 800-401-1583. Answering your question does not create an attorney-client relationship.
I agree with Mr. Cave. Recently, I consulted a young servicemember who was dealing with similar circumstances. I will give you the same advice. You need to retain an attorney as soon as possible who can negotiate with the command on your behalf. Do not waive your board if the command does not offer a General discharge. In the meantime, stay out of trouble. Good luck.