(Seeing as I have a habit of writing incredibly long posts all about myself, I should warn you now that if you're having a bit of trouble with insomnia this might help...)

I can relate a little in regards to PTSD getting in the way with study, I have studied Animal Studies and Companion Animal Services and PTSD definitely had an effect.
The first year I was still dealing with a few things and I ended up having a break down that year. I had an exam around the point of my breakdown and was so messed up that I could barely even hold a pen, let alone read the book. SOMEHOW without even studying I managed to pass. Even my lecturer was shocked when I'd told her I'd never studied and passed (it wasn't an amazing score, around 75% I think).
My lecturer knew about my problems because after I flipped she had to find out. But telling her was the best thing I did because she knew I wasn't making excuses. There were others in the class, people I hung out with, who really made no effort in anything, and that reflected on me.

But when she found out, she was 100% understanding. I remember one morning I had showed up and was feeling pretty crappy. It obviously showed on my face because when my group was worknig with the dogs she told everyone else to clean the runs and she was going to take the dogs to the yard with me. The reason was she wanted to talk to me because it was obvious something was up. I was able to have a bit of a heart to heart with her about things (and where better to have a heart to heart than in a yard with 5 greyhounds trying to run you over).
We also discussed an assignment I had due, we had to do a presentation (I CANNOT to public speaking for the life of me), but my group was making no effort while I had done all this research, so I was worried I was going to fail. She said to me just do what I have to do, and the effort of my group is not going to reflect on my marks because she knows I am committed, even with issues that make it difficult.

Then last year I had to study and work in the vet clinic, but I couldn't answer the phones, and we were being watched by our supervisor the whole time we were serving customers, giving change, working on the computer. Talk about paranoia.
And like I said earlier I couldn't talk in front of the class. The hard part was the judgment of others and pressure to just do it, I could barely cope with it. But again I told my lecturer the truth and they were understanding.

Anyway my point of all this is, if you feel comfortable doing so, perhaps tell them the truth. You don't have to do so, and if you do you don't have to fully go into everything. I just want to explain to you with a bit of my story of studying with PTSD, that you CAN do it, it's not impossible to get your full qualification with something like that.
In my first year I had someone giving me crap, someone who was so convinced she was going back the next year to study vet nursing (all without making any effort or course). She going around asking if she was the only one who didn't like me and why are they talking to me. She lied about me to my friends. She was a cow. Well, my certificate is now happily hanging on my wall, she never even passed, so she never got to go back to be a vet nurse the next year like she was so sure she would. I know I shouldn't be happy about others downfalls, but hey, don't dish it out if you can't learn to take it back.

In fact you may find that people with some issues (PTSD, depression, anxiety, etc.) are more committed than most other people in their class because they have a real determination to win over these traumas. If your lecturer knows a bit, it may give him more understanding, and like with my first lecturer, he may be very supportive. You could also try going to a counselor and telling them so they can explain it to him. Last year I had my lecturer and the counselor with me to discuss ways to make things easier for me.

And I understand being intimidated by some lecturers rather than others, I can't quite put my finger on what it is though. Maybe when I think they are better than me, or I get some thought in my head that they think I'm a total quack purely based on a look on their face that I interpreted using my insecurity that everyone hates me. Who knows... And when I get intimidated I tend to lose my train of thought, I get more blubbery with my words and forget what I was going to say. And, my face goes red. Lord how I dread my face going red. And it's all because one person pointed it out once, so now I can't have a conversation without it because it's subconsciously in my head.

I was terrified of so many aspects of studying, the first day in the clinic I went home with an excruciating stomach ache because my nerves got to me. But giving my lecturers a bit of insight made a world of difference, it didn't solve every problem, it didn't mean I didn't have to try as hard with my study, but it gave me the ability to get through so much easier. I was able to relax a bit knowing I was going to be cut a bit of slack, knowing that things could be done a little differently for me so I could cope emotionally.
If you feel comfortable doing so, I really would suggest giving him some insight. Show him you're committed, show him that your pushing through even with something that would hold a lot of people back. He may admire you for the your commitment.

*cue cheesy motivation music*

"I believe I can fly, I believe I can touch the sky, think about it every night and day, spread my wings and fly away"

Okay I'll stop before I make people sick...