Can you give me advice about this chapter 13 discharge?

I have had medical issues with headaches and migraines after a TBI while overseas "non combat related" coming up on a year now. Shortly after I started to get depressed and get seen for it. I came back home early from my rotation overseas. I got put on a certain medication which made me gain weight very fast and made me oversleep. I missed morning formation after taking this medication 3 times within 3-4 months. Morning formation is 3 miles away and also my transportation was a bicycle but that is not my excuse. My excuse was the medication which I started to take earlier in the day and became very sleepy and started to fall asleep early and wake up a lot earlier then what I needed to. After a month of doing good and not oversleeping I got called in and got a Article 15 and lost rank for missing formation. Ok oh well I didn't fight it so that's not my problem even though I didn't like it. I was counseled 1 time for being overweight and I got taped. This is the second time I was on the program and the first time I got off within a month. Its been about 4 months since the first counseling and they haven't weighed, taped or counseled me since. They kept telling me that I was gonna get a Chapter 18 discharge for being overweight. The process got halted because my PCM referred me to a MEB. That MEB got turned down because " I didn't have enough treatment time". I was unable to go to long distance appointments because I don't have a drivers license and my command was not supporting me with going to my appointments. I got married and after 4 months of not going to see my neurologist because the closest one is 2 hours away the neurologist told me in his opinion I don't meet the medical standard and he is referring me to a MEB. Its been almost 2 weeks now and I only heard from 1 person saying that they are waiting for some medical documents first. He also gave me a permanent profile. I went back and gave my permanent profile to my NCO and told him I got referred to a MEB again by a specialist this time. 7 days later I got called into 1SG's office with the commander and they told me that they are trying to separate me via chapter 13 under honorable conditions for being overweight, missing formation 3 times back in the early part of the year and also having a dirty barracks room one time " they also lied and said that I disobeyed a lawful order to clean my room after that" which I have no idea where they got that from and I don't know how to fight that one. So currently I am pending a MEB. My real question is, can I fight this if the MEB doesn't go through in time or doesn't go through at all? From my understanding if the MEB goes through it overrules a chapter "that's what I heard"?. How can they go from a chapter 18 discharge to a chapter 13? I haven't done anything since missing formation. Ive been getting complimented on the work ive been doing and even though I am in pain half the time with my headaches and migraines I still try to stay positive but I cant really stay positive right now because they are threatening my medical treatment and benefits. Also it will be on my records for life. What can I do? Im still in my 7 day period to talk to legal and I am going this afternoon, can someone give me some guidance please!