Hi Girly. Your post really struck a chord with me.
I don't know if my experience might be helpful to you at all. I'm not claiming to be right about any of this, just how it was for me. I graduated last year with a 2:1 in English (as a very mature student lol) and was only 1.5% off a First at the last knockings. If the penny had dropped sooner, I might have actually got one, but I didn't get the 'argument' thing either for the first couple of years.
Like you, I could read and remember facts and crammed my essays and exam papers full of them. The feedback was always 'impressive knowledge but ....' and I just couldn't figure out where I was going wrong, despite numerous tutorials. I just couldn't get my head around it at all.
Then at the beginning of my third and final year it clicked and my marks shot up. What I eventually realised is that there is almost a formula involved in essay writing and responding to exam questions, and the ones who had mastered that were doing well. As Diamondback wrote earlier, it also helps to know what the individual lecturer wants. I came to realise that this one liked things presented this way, another liked it presented in a different way - it really did vary from lecturer to lecturer. There was one who was especially hot on indexing and bibliographies, the use of quotations etc. and would deduct marks if there were errors. Another wasn't too bothered with all that and would focus on how persuasively I had argued my point, and so on.
What I came to realise that I needed to take an assumption or assertion that has been made about something and then come up with alternatives to it (argue against it) and provide evidence to support my argument. Or alternatively make my own assertion and provide evidence to back it up (argue in favour of it). The first time I got it right - I got 76% for an essay, and even then I wasn't entirely sure why I'd got such a good mark, until eventually I twigged.
I was helped a lot to understand the concept by a fellow student on my course who was doing really well. She was a tremendous help to me, and without her I don't think I would have grasped it still. Is there someone on your course who might be able to help you? I also asked other students if I could read their essays (after they were marked) and this helped me a lot as well. It became clear what the ones who were doing well had in common, and every time it was that they had mastered the 'argument' thing.
Getting as far as you have is an incredible achievement. I know how tough it is when you have kids, work etc, as well as all the study, and if you are on course for a 2.2 then that is still good going and you should be very proud of yourself.