Cristo based on personal experience and stories from friends/acquaintances universities are pretty understanding when it comes to mitigating circumstances. I'd be very surprised if this wasn't the case in your case as you're clearly having a fucking tough time of it at the moment. If you're doing well in all your other modules it will be plain as day to them that you are a capable and hard working student, and they'll try to accommodate for you. It's absolutely in the university's interests for you to graduate, and graduate well at that. I think you should feel positive on this front with regards to it ending well.
At uni I was in a similar situation regarding going into exams absolutely knowing I would fail, albeit in my case it was because I did absolutely no work and not because I'd really challenged myself by picking a difficult module. I went to the exam, opened the paper and couldn't even begin to tackle any of the essay questions, and could choose the three questions I liked best from nine haha. I sat there for ten minutes and realised that I simply couldn't sit there for another 2 hours and 50 minutes. After another five minutes I walked to the front of the hall of four hundred people to collect my bag and jacket before leaving. It was humiliating and still a bad memory. Next time in that situation I didn't go and that was much better than going and trying to go through with something you were guaranteed to fail.
With regards to your girlfriend, just tell her what's going on. When I got kicked out of uni back in 2011 and my depression really went into overdrive I tried to hide it from my family. I knew they'd find out eventually but instead I lied for months.
If she's a good girlfriend, which I'm sure she is, she'll understand and support you. Don't worry about her thinking of you as being weak or less of a man or however you put it, attitudes towards mental health and men showing vulnerabilities have changed. Youre here talking to a bunch of blokes who support the same football team as you, and we're all sharing our own experiences and trying to offer help and support. Times have changed and she won't think of you any differently.
It also won't be a burden on her. I know how big a deal this is to you, but it won't be as big a deal to her. My girlfriend has a health condition that impacts on her day to day life and on her mental health/hapiness. She often apologises because she feels like a burden and a drain on me, but it isn't like that at all. My sole concern is for her happiness and well-being, trying to help her because I don't see her issues as being as insurmountable from the outside looking in, understandably she has to live with it so she often sees it as being an unwinnable fight. She thinks I must see her as being weak because of how she so often struggles, but I actually think she's incredibly strong for coping with her health condition as brilliantly as she does.
As I said I've had some similar issues to yours at university when I first went, and just this summer I finally completed a degree course and am about to start a post grad, so we're at similar points in our lives and I can relate to what you're experiencing. So I'm always happy to talk about that kind of stuff mate.
So yeah, talk to your girlfriend, it's the best thing to do. See your psychologist/get some help, be on the ball about trying to resolve the situation with the uni. Don't go to the exam and cause yourself more distress and maybe even an attack if you are certain you'll fail. Just do your best to forget about the dreaded fucking bastard module. Do things you enjoy, spend time with people you care about and whose company you enjoy, work out, try a new hobby. Do some positive things that will make you feel good.